From 0a0da3f92118950862700497bc7917f0fbf6a6e8 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:24 -0700 Subject: [PATCH 01/33] KVM: Make support for kvm_arch_vcpu_async_ioctl() mandatory Implement kvm_arch_vcpu_async_ioctl() "natively" in x86 and arm64 instead of relying on an #ifdef'd stub, and drop HAVE_KVM_VCPU_ASYNC_IOCTL in anticipation of using the API on x86. Once x86 uses the API, providing a stub for one architecture and having all other architectures opt-in requires more code than simply implementing the API in the lone holdout. Eliminating the Kconfig will also reduce churn if the API is renamed in the future (spoiler alert). No functional change intended. Acked-by: Claudio Imbrenda Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-2-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/arm64/kvm/arm.c | 6 ++++++ arch/loongarch/kvm/Kconfig | 1 - arch/mips/kvm/Kconfig | 1 - arch/powerpc/kvm/Kconfig | 1 - arch/riscv/kvm/Kconfig | 1 - arch/s390/kvm/Kconfig | 1 - arch/x86/kvm/x86.c | 6 ++++++ include/linux/kvm_host.h | 10 ---------- virt/kvm/Kconfig | 3 --- 9 files changed, 12 insertions(+), 18 deletions(-) diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 870953b4a8a7..ef5bf57f79b7 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -1835,6 +1835,12 @@ long kvm_arch_vcpu_ioctl(struct file *filp, return r; } +long kvm_arch_vcpu_async_ioctl(struct file *filp, unsigned int ioctl, + unsigned long arg) +{ + return -ENOIOCTLCMD; +} + void kvm_arch_sync_dirty_log(struct kvm *kvm, struct kvm_memory_slot *memslot) { diff --git a/arch/loongarch/kvm/Kconfig b/arch/loongarch/kvm/Kconfig index ae64bbdf83a7..ed4f724db774 100644 --- a/arch/loongarch/kvm/Kconfig +++ b/arch/loongarch/kvm/Kconfig @@ -25,7 +25,6 @@ config KVM select HAVE_KVM_IRQCHIP select HAVE_KVM_MSI select HAVE_KVM_READONLY_MEM - select HAVE_KVM_VCPU_ASYNC_IOCTL select KVM_COMMON select KVM_GENERIC_DIRTYLOG_READ_PROTECT select KVM_GENERIC_HARDWARE_ENABLING diff --git a/arch/mips/kvm/Kconfig b/arch/mips/kvm/Kconfig index ab57221fa4dd..cc13cc35f208 100644 --- a/arch/mips/kvm/Kconfig +++ b/arch/mips/kvm/Kconfig @@ -22,7 +22,6 @@ config KVM select EXPORT_UASM select KVM_COMMON select KVM_GENERIC_DIRTYLOG_READ_PROTECT - select HAVE_KVM_VCPU_ASYNC_IOCTL select KVM_MMIO select KVM_GENERIC_MMU_NOTIFIER select KVM_GENERIC_HARDWARE_ENABLING diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig index 2f2702c867f7..c9a2d50ff1b0 100644 --- a/arch/powerpc/kvm/Kconfig +++ b/arch/powerpc/kvm/Kconfig @@ -20,7 +20,6 @@ if VIRTUALIZATION config KVM bool select KVM_COMMON - select HAVE_KVM_VCPU_ASYNC_IOCTL select KVM_VFIO select HAVE_KVM_IRQ_BYPASS diff --git a/arch/riscv/kvm/Kconfig b/arch/riscv/kvm/Kconfig index c50328212917..77379f77840a 100644 --- a/arch/riscv/kvm/Kconfig +++ b/arch/riscv/kvm/Kconfig @@ -23,7 +23,6 @@ config KVM select HAVE_KVM_IRQCHIP select HAVE_KVM_IRQ_ROUTING select HAVE_KVM_MSI - select HAVE_KVM_VCPU_ASYNC_IOCTL select HAVE_KVM_READONLY_MEM select HAVE_KVM_DIRTY_RING_ACQ_REL select KVM_COMMON diff --git a/arch/s390/kvm/Kconfig b/arch/s390/kvm/Kconfig index cae908d64550..96d16028e8b7 100644 --- a/arch/s390/kvm/Kconfig +++ b/arch/s390/kvm/Kconfig @@ -20,7 +20,6 @@ config KVM def_tristate y prompt "Kernel-based Virtual Machine (KVM) support" select HAVE_KVM_CPU_RELAX_INTERCEPT - select HAVE_KVM_VCPU_ASYNC_IOCTL select KVM_ASYNC_PF select KVM_ASYNC_PF_SYNC select KVM_COMMON diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index b4b5d2d09634..ca5ba2caf314 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -7240,6 +7240,12 @@ static int kvm_vm_ioctl_set_clock(struct kvm *kvm, void __user *argp) return 0; } +long kvm_arch_vcpu_async_ioctl(struct file *filp, unsigned int ioctl, + unsigned long arg) +{ + return -ENOIOCTLCMD; +} + int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg) { struct kvm *kvm = filp->private_data; diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 5bd76cf394fa..7186b2ae4b57 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -2437,18 +2437,8 @@ static inline bool kvm_arch_no_poll(struct kvm_vcpu *vcpu) } #endif /* CONFIG_HAVE_KVM_NO_POLL */ -#ifdef CONFIG_HAVE_KVM_VCPU_ASYNC_IOCTL long kvm_arch_vcpu_async_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg); -#else -static inline long kvm_arch_vcpu_async_ioctl(struct file *filp, - unsigned int ioctl, - unsigned long arg) -{ - return -ENOIOCTLCMD; -} -#endif /* CONFIG_HAVE_KVM_VCPU_ASYNC_IOCTL */ - void kvm_arch_guest_memory_reclaimed(struct kvm *kvm); #ifdef CONFIG_HAVE_KVM_VCPU_RUN_PID_CHANGE diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig index 5f0015c5dd95..267c7369c765 100644 --- a/virt/kvm/Kconfig +++ b/virt/kvm/Kconfig @@ -78,9 +78,6 @@ config HAVE_KVM_IRQ_BYPASS tristate select IRQ_BYPASS_MANAGER -config HAVE_KVM_VCPU_ASYNC_IOCTL - bool - config HAVE_KVM_VCPU_RUN_PID_CHANGE bool From 50efc2340a598da4bafa40bc01e18f8cf73a4ae3 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:25 -0700 Subject: [PATCH 02/33] KVM: Rename kvm_arch_vcpu_async_ioctl() to kvm_arch_vcpu_unlocked_ioctl() Rename the "async" ioctl API to "unlocked" so that upcoming usage in x86's TDX code doesn't result in a massive misnomer. To avoid having to retry SEAMCALLs, TDX needs to acquire kvm->lock *and* all vcpu->mutex locks, and acquiring all of those locks after/inside the current vCPU's mutex is a non-starter. However, TDX also needs to acquire the vCPU's mutex and load the vCPU, i.e. the handling is very much not async to the vCPU. No functional change intended. Acked-by: Claudio Imbrenda Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-3-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/arm64/kvm/arm.c | 4 ++-- arch/loongarch/kvm/vcpu.c | 4 ++-- arch/mips/kvm/mips.c | 4 ++-- arch/powerpc/kvm/powerpc.c | 4 ++-- arch/riscv/kvm/vcpu.c | 4 ++-- arch/s390/kvm/kvm-s390.c | 4 ++-- arch/x86/kvm/x86.c | 4 ++-- include/linux/kvm_host.h | 4 ++-- virt/kvm/kvm_main.c | 6 +++--- 9 files changed, 19 insertions(+), 19 deletions(-) diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index ef5bf57f79b7..cf23f6b07ec7 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -1835,8 +1835,8 @@ long kvm_arch_vcpu_ioctl(struct file *filp, return r; } -long kvm_arch_vcpu_async_ioctl(struct file *filp, unsigned int ioctl, - unsigned long arg) +long kvm_arch_vcpu_unlocked_ioctl(struct file *filp, unsigned int ioctl, + unsigned long arg) { return -ENOIOCTLCMD; } diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c index 30e3b089a596..9a5844e85fd3 100644 --- a/arch/loongarch/kvm/vcpu.c +++ b/arch/loongarch/kvm/vcpu.c @@ -1471,8 +1471,8 @@ int kvm_vcpu_ioctl_interrupt(struct kvm_vcpu *vcpu, struct kvm_interrupt *irq) return 0; } -long kvm_arch_vcpu_async_ioctl(struct file *filp, - unsigned int ioctl, unsigned long arg) +long kvm_arch_vcpu_unlocked_ioctl(struct file *filp, unsigned int ioctl, + unsigned long arg) { void __user *argp = (void __user *)arg; struct kvm_vcpu *vcpu = filp->private_data; diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c index a75587018f44..b0fb92fda4d4 100644 --- a/arch/mips/kvm/mips.c +++ b/arch/mips/kvm/mips.c @@ -895,8 +895,8 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu, return r; } -long kvm_arch_vcpu_async_ioctl(struct file *filp, unsigned int ioctl, - unsigned long arg) +long kvm_arch_vcpu_unlocked_ioctl(struct file *filp, unsigned int ioctl, + unsigned long arg) { struct kvm_vcpu *vcpu = filp->private_data; void __user *argp = (void __user *)arg; diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c index 2ba057171ebe..9a89a6d98f97 100644 --- a/arch/powerpc/kvm/powerpc.c +++ b/arch/powerpc/kvm/powerpc.c @@ -2028,8 +2028,8 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu, return -EINVAL; } -long kvm_arch_vcpu_async_ioctl(struct file *filp, - unsigned int ioctl, unsigned long arg) +long kvm_arch_vcpu_unlocked_ioctl(struct file *filp, unsigned int ioctl, + unsigned long arg) { struct kvm_vcpu *vcpu = filp->private_data; void __user *argp = (void __user *)arg; diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c index bccb919ca615..a4bd6077eecc 100644 --- a/arch/riscv/kvm/vcpu.c +++ b/arch/riscv/kvm/vcpu.c @@ -238,8 +238,8 @@ vm_fault_t kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf) return VM_FAULT_SIGBUS; } -long kvm_arch_vcpu_async_ioctl(struct file *filp, - unsigned int ioctl, unsigned long arg) +long kvm_arch_vcpu_unlocked_ioctl(struct file *filp, unsigned int ioctl, + unsigned long arg) { struct kvm_vcpu *vcpu = filp->private_data; void __user *argp = (void __user *)arg; diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 16ba04062854..8c4caa5f2fcd 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -5730,8 +5730,8 @@ static long kvm_s390_vcpu_memsida_op(struct kvm_vcpu *vcpu, return r; } -long kvm_arch_vcpu_async_ioctl(struct file *filp, - unsigned int ioctl, unsigned long arg) +long kvm_arch_vcpu_unlocked_ioctl(struct file *filp, unsigned int ioctl, + unsigned long arg) { struct kvm_vcpu *vcpu = filp->private_data; void __user *argp = (void __user *)arg; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index ca5ba2caf314..b85cb213a336 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -7240,8 +7240,8 @@ static int kvm_vm_ioctl_set_clock(struct kvm *kvm, void __user *argp) return 0; } -long kvm_arch_vcpu_async_ioctl(struct file *filp, unsigned int ioctl, - unsigned long arg) +long kvm_arch_vcpu_unlocked_ioctl(struct file *filp, unsigned int ioctl, + unsigned long arg) { return -ENOIOCTLCMD; } diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 7186b2ae4b57..d93f75b05ae2 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -1557,6 +1557,8 @@ long kvm_arch_dev_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg); long kvm_arch_vcpu_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg); +long kvm_arch_vcpu_unlocked_ioctl(struct file *filp, + unsigned int ioctl, unsigned long arg); vm_fault_t kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf); int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext); @@ -2437,8 +2439,6 @@ static inline bool kvm_arch_no_poll(struct kvm_vcpu *vcpu) } #endif /* CONFIG_HAVE_KVM_NO_POLL */ -long kvm_arch_vcpu_async_ioctl(struct file *filp, - unsigned int ioctl, unsigned long arg); void kvm_arch_guest_memory_reclaimed(struct kvm *kvm); #ifdef CONFIG_HAVE_KVM_VCPU_RUN_PID_CHANGE diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index b7a0ae2a7b20..b7db1d5f71a8 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -4434,10 +4434,10 @@ static long kvm_vcpu_ioctl(struct file *filp, return r; /* - * Some architectures have vcpu ioctls that are asynchronous to vcpu - * execution; mutex_lock() would break them. + * Let arch code handle select vCPU ioctls without holding vcpu->mutex, + * e.g. to support ioctls that can run asynchronous to vCPU execution. */ - r = kvm_arch_vcpu_async_ioctl(filp, ioctl, arg); + r = kvm_arch_vcpu_unlocked_ioctl(filp, ioctl, arg); if (r != -ENOIOCTLCMD) return r; From 5294a4b93e07ab74ef334434b927a5a33aa0ecfe Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:26 -0700 Subject: [PATCH 03/33] KVM: TDX: Drop PROVE_MMU=y sanity check on to-be-populated mappings Drop TDX's sanity check that a mirror EPT mapping isn't zapped between creating said mapping and doing TDH.MEM.PAGE.ADD, as the check is simultaneously superfluous and incomplete. Per commit 2608f1057601 ("KVM: x86/tdp_mmu: Add a helper function to walk down the TDP MMU"), the justification for introducing kvm_tdp_mmu_gpa_is_mapped() was to check that the target gfn was pre-populated, with a link that points to this snippet: : > One small question: : > : > What if the memory region passed to KVM_TDX_INIT_MEM_REGION hasn't been pre- : > populated? If we want to make KVM_TDX_INIT_MEM_REGION work with these regions, : > then we still need to do the real map. Or we can make KVM_TDX_INIT_MEM_REGION : > return error when it finds the region hasn't been pre-populated? : : Return an error. I don't love the idea of bleeding so many TDX details into : userspace, but I'm pretty sure that ship sailed a long, long time ago. But that justification makes little sense for the final code, as the check on nr_premapped after TDH.MEM.PAGE.ADD will detect and return an error if KVM attempted to zap a S-EPT entry (tdx_sept_zap_private_spte() will fail on TDH.MEM.RANGE.BLOCK due lack of a valid S-EPT entry). And as evidenced by the "is mapped?" code being guarded with CONFIG_KVM_PROVE_MMU=y, KVM is NOT relying on the check for general correctness. The sanity check is also incomplete in the sense that mmu_lock is dropped between the check and TDH.MEM.PAGE.ADD, i.e. will only detect KVM bugs that zap SPTEs in a very specific window (note, this also applies to the check on nr_premapped). Removing the sanity check will allow removing kvm_tdp_mmu_gpa_is_mapped(), which has no business being exposed to vendor code, and more importantly will pave the way for eliminating the "pre-map" approach entirely in favor of doing TDH.MEM.PAGE.ADD under mmu_lock. Reviewed-by: Ira Weiny Reviewed-by: Kai Huang Reviewed-by: Binbin Wu Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-4-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 14 -------------- 1 file changed, 14 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 0a49c863c811..e59705da2779 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -3191,20 +3191,6 @@ static int tdx_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, if (ret < 0) goto out; - /* - * The private mem cannot be zapped after kvm_tdp_map_page() - * because all paths are covered by slots_lock and the - * filemap invalidate lock. Check that they are indeed enough. - */ - if (IS_ENABLED(CONFIG_KVM_PROVE_MMU)) { - scoped_guard(read_lock, &kvm->mmu_lock) { - if (KVM_BUG_ON(!kvm_tdp_mmu_gpa_is_mapped(vcpu, gpa), kvm)) { - ret = -EIO; - goto out; - } - } - } - ret = 0; err = tdh_mem_page_add(&kvm_tdx->td, gpa, pfn_to_page(pfn), src_page, &entry, &level_state); From 3ab3283dbb2c1246cbabdba8f3c52e72a3d88121 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:27 -0700 Subject: [PATCH 04/33] KVM: x86/mmu: Add dedicated API to map guest_memfd pfn into TDP MMU Add and use a new API for mapping a private pfn from guest_memfd into the TDP MMU from TDX's post-populate hook instead of partially open-coding the functionality into the TDX code. Sharing code with the pre-fault path sounded good on paper, but it's fatally flawed as simulating a fault loses the pfn, and calling back into gmem to re-retrieve the pfn creates locking problems, e.g. kvm_gmem_populate() already holds the gmem invalidation lock. Providing a dedicated API will also removing several MMU exports that ideally would not be exposed outside of the MMU, let alone to vendor code. On that topic, opportunistically drop the kvm_mmu_load() export. Leave kvm_tdp_mmu_gpa_is_mapped() alone for now; the entire commit that added kvm_tdp_mmu_gpa_is_mapped() will be removed in the near future. Gate the API on CONFIG_KVM_GUEST_MEMFD=y as private memory _must_ be backed by guest_memfd. Add a lockdep-only assert to that the incoming pfn is indeed backed by guest_memfd, and that the gmem instance's invalidate lock is held (which, combined with slots_lock being held, obviates the need to check for a stale "fault"). Cc: Michael Roth Cc: Yan Zhao Cc: Ira Weiny Cc: Vishal Annapurve Cc: Rick Edgecombe Reviewed-by: Rick Edgecombe Reviewed-by: Kai Huang Link: https://lore.kernel.org/all/20250709232103.zwmufocd3l7sqk7y@amd.com Reviewed-by: Binbin Wu Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-5-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/mmu.h | 1 + arch/x86/kvm/mmu/mmu.c | 81 +++++++++++++++++++++++++++++++++++++++++- arch/x86/kvm/vmx/tdx.c | 10 ++---- 3 files changed, 84 insertions(+), 8 deletions(-) diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h index f63074048ec6..2f108e381959 100644 --- a/arch/x86/kvm/mmu.h +++ b/arch/x86/kvm/mmu.h @@ -259,6 +259,7 @@ extern bool tdp_mmu_enabled; bool kvm_tdp_mmu_gpa_is_mapped(struct kvm_vcpu *vcpu, u64 gpa); int kvm_tdp_map_page(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code, u8 *level); +int kvm_tdp_mmu_map_private_pfn(struct kvm_vcpu *vcpu, gfn_t gfn, kvm_pfn_t pfn); static inline bool kvm_memslots_have_rmaps(struct kvm *kvm) { diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 667d66cf76d5..d24fa59f872b 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -5014,6 +5014,86 @@ long kvm_arch_vcpu_pre_fault_memory(struct kvm_vcpu *vcpu, return min(range->size, end - range->gpa); } +#ifdef CONFIG_KVM_GUEST_MEMFD +static void kvm_assert_gmem_invalidate_lock_held(struct kvm_memory_slot *slot) +{ +#ifdef CONFIG_PROVE_LOCKING + if (WARN_ON_ONCE(!kvm_slot_has_gmem(slot)) || + WARN_ON_ONCE(!slot->gmem.file) || + WARN_ON_ONCE(!file_count(slot->gmem.file))) + return; + + lockdep_assert_held(&file_inode(slot->gmem.file)->i_mapping->invalidate_lock); +#endif +} + +int kvm_tdp_mmu_map_private_pfn(struct kvm_vcpu *vcpu, gfn_t gfn, kvm_pfn_t pfn) +{ + struct kvm_page_fault fault = { + .addr = gfn_to_gpa(gfn), + .error_code = PFERR_GUEST_FINAL_MASK | PFERR_PRIVATE_ACCESS, + .prefetch = true, + .is_tdp = true, + .nx_huge_page_workaround_enabled = is_nx_huge_page_enabled(vcpu->kvm), + + .max_level = PG_LEVEL_4K, + .req_level = PG_LEVEL_4K, + .goal_level = PG_LEVEL_4K, + .is_private = true, + + .gfn = gfn, + .slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn), + .pfn = pfn, + .map_writable = true, + }; + struct kvm *kvm = vcpu->kvm; + int r; + + lockdep_assert_held(&kvm->slots_lock); + + /* + * Mapping a pre-determined private pfn is intended only for use when + * populating a guest_memfd instance. Assert that the slot is backed + * by guest_memfd and that the gmem instance's invalidate_lock is held. + */ + kvm_assert_gmem_invalidate_lock_held(fault.slot); + + if (KVM_BUG_ON(!tdp_mmu_enabled, kvm)) + return -EIO; + + if (kvm_gfn_is_write_tracked(kvm, fault.slot, fault.gfn)) + return -EPERM; + + r = kvm_mmu_reload(vcpu); + if (r) + return r; + + r = mmu_topup_memory_caches(vcpu, false); + if (r) + return r; + + do { + if (signal_pending(current)) + return -EINTR; + + if (kvm_test_request(KVM_REQ_VM_DEAD, vcpu)) + return -EIO; + + cond_resched(); + + guard(read_lock)(&kvm->mmu_lock); + + r = kvm_tdp_mmu_map(vcpu, &fault); + } while (r == RET_PF_RETRY); + + if (r != RET_PF_FIXED) + return -EIO; + + return 0; +} +EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_tdp_mmu_map_private_pfn); +#endif + static void nonpaging_init_context(struct kvm_mmu *context) { context->page_fault = nonpaging_page_fault; @@ -5997,7 +6077,6 @@ int kvm_mmu_load(struct kvm_vcpu *vcpu) out: return r; } -EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_mmu_load); void kvm_mmu_unload(struct kvm_vcpu *vcpu) { diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index e59705da2779..4e712e11e00c 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -3167,15 +3167,12 @@ struct tdx_gmem_post_populate_arg { static int tdx_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, void __user *src, int order, void *_arg) { - u64 error_code = PFERR_GUEST_FINAL_MASK | PFERR_PRIVATE_ACCESS; - struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm); struct tdx_gmem_post_populate_arg *arg = _arg; - struct kvm_vcpu *vcpu = arg->vcpu; + struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm); + u64 err, entry, level_state; gpa_t gpa = gfn_to_gpa(gfn); - u8 level = PG_LEVEL_4K; struct page *src_page; int ret, i; - u64 err, entry, level_state; /* * Get the source page if it has been faulted in. Return failure if the @@ -3187,7 +3184,7 @@ static int tdx_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, if (ret != 1) return -ENOMEM; - ret = kvm_tdp_map_page(vcpu, gpa, error_code, &level); + ret = kvm_tdp_mmu_map_private_pfn(arg->vcpu, gfn, pfn); if (ret < 0) goto out; @@ -3250,7 +3247,6 @@ static int tdx_vcpu_init_mem_region(struct kvm_vcpu *vcpu, struct kvm_tdx_cmd *c !vt_is_tdx_private_gpa(kvm, region.gpa + (region.nr_pages << PAGE_SHIFT) - 1)) return -EINVAL; - kvm_mmu_reload(vcpu); ret = 0; while (region.nr_pages) { if (signal_pending(current)) { From c1f173fb3389d39f78fc57f14b767e7127bc3908 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:28 -0700 Subject: [PATCH 05/33] KVM: x86/mmu: WARN if KVM attempts to map into an invalid TDP MMU root When mapping into the TDP MMU, WARN (if KVM_PROVE_MMU=y) if the root is invalid, e.g. if KVM is attempting to insert a mapping without checking if the information and MMU context is fresh. Reviewed-by: Kai Huang Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-6-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/mmu/tdp_mmu.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index c5734ca5c17d..440fd8f80397 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -1273,6 +1273,8 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) struct kvm_mmu_page *sp; int ret = RET_PF_RETRY; + KVM_MMU_WARN_ON(!root || root->role.invalid); + kvm_mmu_hugepage_adjust(vcpu, fault); trace_kvm_mmu_spte_requested(fault); From fe7413e39810235fc812d5d85053cb1957388090 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:29 -0700 Subject: [PATCH 06/33] Revert "KVM: x86/tdp_mmu: Add a helper function to walk down the TDP MMU" Remove the helper and exports that were added to allow TDX code to reuse kvm_tdp_map_page() for its gmem post-populate flow now that a dedicated TDP MMU API is provided to install a mapping given a gfn+pfn pair. This reverts commit 2608f105760115e94a03efd9f12f8fbfd1f9af4b. Reviewed-by: Rick Edgecombe Reviewed-by: Binbin Wu Reviewed-by: Kai Huang Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-7-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/mmu.h | 2 -- arch/x86/kvm/mmu/mmu.c | 4 ++-- arch/x86/kvm/mmu/tdp_mmu.c | 37 +++++-------------------------------- 3 files changed, 7 insertions(+), 36 deletions(-) diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h index 2f108e381959..9e5045a60d8b 100644 --- a/arch/x86/kvm/mmu.h +++ b/arch/x86/kvm/mmu.h @@ -257,8 +257,6 @@ extern bool tdp_mmu_enabled; #define tdp_mmu_enabled false #endif -bool kvm_tdp_mmu_gpa_is_mapped(struct kvm_vcpu *vcpu, u64 gpa); -int kvm_tdp_map_page(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code, u8 *level); int kvm_tdp_mmu_map_private_pfn(struct kvm_vcpu *vcpu, gfn_t gfn, kvm_pfn_t pfn); static inline bool kvm_memslots_have_rmaps(struct kvm *kvm) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index d24fa59f872b..559c80c841b9 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -4924,7 +4924,8 @@ int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) return direct_page_fault(vcpu, fault); } -int kvm_tdp_map_page(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code, u8 *level) +static int kvm_tdp_map_page(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code, + u8 *level) { int r; @@ -4966,7 +4967,6 @@ int kvm_tdp_map_page(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code, u8 *level return -EIO; } } -EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_tdp_map_page); long kvm_arch_vcpu_pre_fault_memory(struct kvm_vcpu *vcpu, struct kvm_pre_fault_memory *range) diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index 440fd8f80397..e735d2f8367b 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -1941,13 +1941,16 @@ bool kvm_tdp_mmu_write_protect_gfn(struct kvm *kvm, * * Must be called between kvm_tdp_mmu_walk_lockless_{begin,end}. */ -static int __kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, - struct kvm_mmu_page *root) +int kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, + int *root_level) { + struct kvm_mmu_page *root = root_to_sp(vcpu->arch.mmu->root.hpa); struct tdp_iter iter; gfn_t gfn = addr >> PAGE_SHIFT; int leaf = -1; + *root_level = vcpu->arch.mmu->root_role.level; + for_each_tdp_pte(iter, vcpu->kvm, root, gfn, gfn + 1) { leaf = iter.level; sptes[leaf] = iter.old_spte; @@ -1956,36 +1959,6 @@ static int __kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, return leaf; } -int kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, - int *root_level) -{ - struct kvm_mmu_page *root = root_to_sp(vcpu->arch.mmu->root.hpa); - *root_level = vcpu->arch.mmu->root_role.level; - - return __kvm_tdp_mmu_get_walk(vcpu, addr, sptes, root); -} - -bool kvm_tdp_mmu_gpa_is_mapped(struct kvm_vcpu *vcpu, u64 gpa) -{ - struct kvm *kvm = vcpu->kvm; - bool is_direct = kvm_is_addr_direct(kvm, gpa); - hpa_t root = is_direct ? vcpu->arch.mmu->root.hpa : - vcpu->arch.mmu->mirror_root_hpa; - u64 sptes[PT64_ROOT_MAX_LEVEL + 1], spte; - int leaf; - - lockdep_assert_held(&kvm->mmu_lock); - rcu_read_lock(); - leaf = __kvm_tdp_mmu_get_walk(vcpu, gpa, sptes, root_to_sp(root)); - rcu_read_unlock(); - if (leaf < 0) - return false; - - spte = sptes[leaf]; - return is_shadow_present_pte(spte) && is_last_spte(spte, leaf); -} -EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_tdp_mmu_gpa_is_mapped); - /* * Returns the last level spte pointer of the shadow page walk for the given * gpa, and sets *spte to the spte value. This spte may be non-preset. If no From 6de2fb089bb27c2c03ca838f2478a659c826d686 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:30 -0700 Subject: [PATCH 07/33] KVM: x86/mmu: Rename kvm_tdp_map_page() to kvm_tdp_page_prefault() Rename kvm_tdp_map_page() to kvm_tdp_page_prefault() now that it's used only by kvm_arch_vcpu_pre_fault_memory(). No functional change intended. Reviewed-by: Rick Edgecombe Reviewed-by: Binbin Wu Reviewed-by: Kai Huang Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-8-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/mmu/mmu.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 559c80c841b9..f5fb12ea04c1 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -4924,8 +4924,8 @@ int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) return direct_page_fault(vcpu, fault); } -static int kvm_tdp_map_page(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code, - u8 *level) +static int kvm_tdp_page_prefault(struct kvm_vcpu *vcpu, gpa_t gpa, + u64 error_code, u8 *level) { int r; @@ -5002,7 +5002,7 @@ long kvm_arch_vcpu_pre_fault_memory(struct kvm_vcpu *vcpu, * Shadow paging uses GVA for kvm page fault, so restrict to * two-dimensional paging. */ - r = kvm_tdp_map_page(vcpu, range->gpa | direct_bits, error_code, &level); + r = kvm_tdp_page_prefault(vcpu, range->gpa | direct_bits, error_code, &level); if (r < 0) return r; From ce7b5695397b54677ed827e0d52058daaecad2a1 Mon Sep 17 00:00:00 2001 From: Yan Zhao Date: Thu, 30 Oct 2025 13:09:31 -0700 Subject: [PATCH 08/33] KVM: TDX: Drop superfluous page pinning in S-EPT management Don't explicitly pin pages when mapping pages into the S-EPT, guest_memfd doesn't support page migration in any capacity, i.e. there are no migrate callbacks because guest_memfd pages *can't* be migrated. See the WARN in kvm_gmem_migrate_folio(). Eliminating TDX's explicit pinning will also enable guest_memfd to support in-place conversion between shared and private memory[1][2]. Because KVM cannot distinguish between speculative/transient refcounts and the intentional refcount for TDX on private pages[3], failing to release private page refcount in TDX could cause guest_memfd to indefinitely wait on decreasing the refcount for the splitting. Under normal conditions, not holding an extra page refcount in TDX is safe because guest_memfd ensures pages are retained until its invalidation notification to KVM MMU is completed. However, if there're bugs in KVM/TDX module, not holding an extra refcount when a page is mapped in S-EPT could result in a page being released from guest_memfd while still mapped in the S-EPT. But, doing work to make a fatal error slightly less fatal is a net negative when that extra work adds complexity and confusion. Several approaches were considered to address the refcount issue, including - Attempting to modify the KVM unmap operation to return a failure, which was deemed too complex and potentially incorrect[4]. - Increasing the folio reference count only upon S-EPT zapping failure[5]. - Use page flags or page_ext to indicate a page is still used by TDX[6], which does not work for HVO (HugeTLB Vmemmap Optimization). - Setting HWPOISON bit or leveraging folio_set_hugetlb_hwpoison()[7]. Due to the complexity or inappropriateness of these approaches, and the fact that S-EPT zapping failure is currently only possible when there are bugs in the KVM or TDX module, which is very rare in a production kernel, a straightforward approach of simply not holding the page reference count in TDX was chosen[8]. When S-EPT zapping errors occur, KVM_BUG_ON() is invoked to kick off all vCPUs and mark the VM as dead. Although there is a potential window that a private page mapped in the S-EPT could be reallocated and used outside the VM, the loud warning from KVM_BUG_ON() should provide sufficient debug information. To be robust against bugs, the user can enable panic_on_warn as normal. Link: https://lore.kernel.org/all/cover.1747264138.git.ackerleytng@google.com [1] Link: https://youtu.be/UnBKahkAon4 [2] Link: https://lore.kernel.org/all/CAGtprH_ypohFy9TOJ8Emm_roT4XbQUtLKZNFcM6Fr+fhTFkE0Q@mail.gmail.com [3] Link: https://lore.kernel.org/all/aEEEJbTzlncbRaRA@yzhao56-desk.sh.intel.com [4] Link: https://lore.kernel.org/all/aE%2Fq9VKkmaCcuwpU@yzhao56-desk.sh.intel.com [5] Link: https://lore.kernel.org/all/aFkeBtuNBN1RrDAJ@yzhao56-desk.sh.intel.com [6] Link: https://lore.kernel.org/all/diqzy0tikran.fsf@ackerleytng-ctop.c.googlers.com [7] Link: https://lore.kernel.org/all/53ea5239f8ef9d8df9af593647243c10435fd219.camel@intel.com [8] Suggested-by: Vishal Annapurve Suggested-by: Ackerley Tng Suggested-by: Rick Edgecombe Signed-off-by: Yan Zhao Reviewed-by: Ira Weiny Reviewed-by: Kai Huang [sean: extract out of hugepage series, massage changelog accordingly] Reviewed-by: Binbin Wu Reviewed-by: Rick Edgecombe Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-9-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 28 ++++------------------------ 1 file changed, 4 insertions(+), 24 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 4e712e11e00c..0935c3aaaea0 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -1583,29 +1583,22 @@ void tdx_load_mmu_pgd(struct kvm_vcpu *vcpu, hpa_t root_hpa, int pgd_level) td_vmcs_write64(to_tdx(vcpu), SHARED_EPT_POINTER, root_hpa); } -static void tdx_unpin(struct kvm *kvm, struct page *page) -{ - put_page(page); -} - static int tdx_mem_page_aug(struct kvm *kvm, gfn_t gfn, - enum pg_level level, struct page *page) + enum pg_level level, kvm_pfn_t pfn) { int tdx_level = pg_level_to_tdx_sept_level(level); struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm); + struct page *page = pfn_to_page(pfn); gpa_t gpa = gfn_to_gpa(gfn); u64 entry, level_state; u64 err; err = tdh_mem_page_aug(&kvm_tdx->td, gpa, tdx_level, page, &entry, &level_state); - if (unlikely(tdx_operand_busy(err))) { - tdx_unpin(kvm, page); + if (unlikely(tdx_operand_busy(err))) return -EBUSY; - } if (KVM_BUG_ON(err, kvm)) { pr_tdx_error_2(TDH_MEM_PAGE_AUG, err, entry, level_state); - tdx_unpin(kvm, page); return -EIO; } @@ -1639,29 +1632,18 @@ static int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn, enum pg_level level, kvm_pfn_t pfn) { struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm); - struct page *page = pfn_to_page(pfn); /* TODO: handle large pages. */ if (KVM_BUG_ON(level != PG_LEVEL_4K, kvm)) return -EINVAL; - /* - * Because guest_memfd doesn't support page migration with - * a_ops->migrate_folio (yet), no callback is triggered for KVM on page - * migration. Until guest_memfd supports page migration, prevent page - * migration. - * TODO: Once guest_memfd introduces callback on page migration, - * implement it and remove get_page/put_page(). - */ - get_page(page); - /* * Read 'pre_fault_allowed' before 'kvm_tdx->state'; see matching * barrier in tdx_td_finalize(). */ smp_rmb(); if (likely(kvm_tdx->state == TD_STATE_RUNNABLE)) - return tdx_mem_page_aug(kvm, gfn, level, page); + return tdx_mem_page_aug(kvm, gfn, level, pfn); return tdx_mem_page_record_premap_cnt(kvm, gfn, level, pfn); } @@ -1712,7 +1694,6 @@ static int tdx_sept_drop_private_spte(struct kvm *kvm, gfn_t gfn, return -EIO; } tdx_quirk_reset_page(page); - tdx_unpin(kvm, page); return 0; } @@ -1792,7 +1773,6 @@ static int tdx_sept_zap_private_spte(struct kvm *kvm, gfn_t gfn, if (tdx_is_sept_zap_err_due_to_premap(kvm_tdx, err, entry, level) && !KVM_BUG_ON(!atomic64_read(&kvm_tdx->nr_premapped), kvm)) { atomic64_dec(&kvm_tdx->nr_premapped); - tdx_unpin(kvm, page); return 0; } From e6348c90dda9cb7beeda1ce83eed6177e46830d2 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:32 -0700 Subject: [PATCH 09/33] KVM: TDX: Return -EIO, not -EINVAL, on a KVM_BUG_ON() condition Return -EIO when a KVM_BUG_ON() is tripped, as KVM's ABI is to return -EIO when a VM has been killed due to a KVM bug, not -EINVAL. Note, many (all?) of the affected paths never propagate the error code to userspace, i.e. this is about internal consistency more than anything else. Reviewed-by: Rick Edgecombe Reviewed-by: Ira Weiny Reviewed-by: Binbin Wu Reviewed-by: Kai Huang Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-10-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 0935c3aaaea0..052a086335f9 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -1621,7 +1621,7 @@ static int tdx_mem_page_record_premap_cnt(struct kvm *kvm, gfn_t gfn, struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm); if (KVM_BUG_ON(kvm->arch.pre_fault_allowed, kvm)) - return -EINVAL; + return -EIO; /* nr_premapped will be decreased when tdh_mem_page_add() is called. */ atomic64_inc(&kvm_tdx->nr_premapped); @@ -1635,7 +1635,7 @@ static int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn, /* TODO: handle large pages. */ if (KVM_BUG_ON(level != PG_LEVEL_4K, kvm)) - return -EINVAL; + return -EIO; /* * Read 'pre_fault_allowed' before 'kvm_tdx->state'; see matching @@ -1658,10 +1658,10 @@ static int tdx_sept_drop_private_spte(struct kvm *kvm, gfn_t gfn, /* TODO: handle large pages. */ if (KVM_BUG_ON(level != PG_LEVEL_4K, kvm)) - return -EINVAL; + return -EIO; if (KVM_BUG_ON(!is_hkid_assigned(kvm_tdx), kvm)) - return -EINVAL; + return -EIO; /* * When zapping private page, write lock is held. So no race condition @@ -1846,7 +1846,7 @@ static int tdx_sept_free_private_spt(struct kvm *kvm, gfn_t gfn, * and slot move/deletion. */ if (KVM_BUG_ON(is_hkid_assigned(kvm_tdx), kvm)) - return -EINVAL; + return -EIO; /* * The HKID assigned to this TD was already freed and cache was @@ -1867,7 +1867,7 @@ static int tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn, * there can't be anything populated in the private EPT. */ if (KVM_BUG_ON(!is_hkid_assigned(to_kvm_tdx(kvm)), kvm)) - return -EINVAL; + return -EIO; ret = tdx_sept_zap_private_spte(kvm, gfn, level, page); if (ret <= 0) From b836503300dcc0d60f7ffc359f0768cd545d8ef9 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:33 -0700 Subject: [PATCH 10/33] KVM: TDX: Fold tdx_sept_drop_private_spte() into tdx_sept_remove_private_spte() Fold tdx_sept_drop_private_spte() into tdx_sept_remove_private_spte() as a step towards having "remove" be the one and only function that deals with removing/zapping/dropping a SPTE, e.g. to avoid having to differentiate between "zap", "drop", and "remove". Eliminating the "drop" helper also gets rid of what is effectively dead code due to redundant checks, e.g. on an HKID being assigned. No functional change intended. Reviewed-by: Binbin Wu Reviewed-by: Kai Huang Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-11-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 90 +++++++++++++++++++----------------------- 1 file changed, 40 insertions(+), 50 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 052a086335f9..667cd089eec8 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -1648,55 +1648,6 @@ static int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn, return tdx_mem_page_record_premap_cnt(kvm, gfn, level, pfn); } -static int tdx_sept_drop_private_spte(struct kvm *kvm, gfn_t gfn, - enum pg_level level, struct page *page) -{ - int tdx_level = pg_level_to_tdx_sept_level(level); - struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm); - gpa_t gpa = gfn_to_gpa(gfn); - u64 err, entry, level_state; - - /* TODO: handle large pages. */ - if (KVM_BUG_ON(level != PG_LEVEL_4K, kvm)) - return -EIO; - - if (KVM_BUG_ON(!is_hkid_assigned(kvm_tdx), kvm)) - return -EIO; - - /* - * When zapping private page, write lock is held. So no race condition - * with other vcpu sept operation. - * Race with TDH.VP.ENTER due to (0-step mitigation) and Guest TDCALLs. - */ - err = tdh_mem_page_remove(&kvm_tdx->td, gpa, tdx_level, &entry, - &level_state); - - if (unlikely(tdx_operand_busy(err))) { - /* - * The second retry is expected to succeed after kicking off all - * other vCPUs and prevent them from invoking TDH.VP.ENTER. - */ - tdx_no_vcpus_enter_start(kvm); - err = tdh_mem_page_remove(&kvm_tdx->td, gpa, tdx_level, &entry, - &level_state); - tdx_no_vcpus_enter_stop(kvm); - } - - if (KVM_BUG_ON(err, kvm)) { - pr_tdx_error_2(TDH_MEM_PAGE_REMOVE, err, entry, level_state); - return -EIO; - } - - err = tdh_phymem_page_wbinvd_hkid((u16)kvm_tdx->hkid, page); - - if (KVM_BUG_ON(err, kvm)) { - pr_tdx_error(TDH_PHYMEM_PAGE_WBINVD, err); - return -EIO; - } - tdx_quirk_reset_page(page); - return 0; -} - static int tdx_sept_link_private_spt(struct kvm *kvm, gfn_t gfn, enum pg_level level, void *private_spt) { @@ -1858,7 +1809,11 @@ static int tdx_sept_free_private_spt(struct kvm *kvm, gfn_t gfn, static int tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn, enum pg_level level, kvm_pfn_t pfn) { + int tdx_level = pg_level_to_tdx_sept_level(level); + struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm); struct page *page = pfn_to_page(pfn); + gpa_t gpa = gfn_to_gpa(gfn); + u64 err, entry, level_state; int ret; /* @@ -1869,6 +1824,10 @@ static int tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn, if (KVM_BUG_ON(!is_hkid_assigned(to_kvm_tdx(kvm)), kvm)) return -EIO; + /* TODO: handle large pages. */ + if (KVM_BUG_ON(level != PG_LEVEL_4K, kvm)) + return -EIO; + ret = tdx_sept_zap_private_spte(kvm, gfn, level, page); if (ret <= 0) return ret; @@ -1879,7 +1838,38 @@ static int tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn, */ tdx_track(kvm); - return tdx_sept_drop_private_spte(kvm, gfn, level, page); + /* + * When zapping private page, write lock is held. So no race condition + * with other vcpu sept operation. + * Race with TDH.VP.ENTER due to (0-step mitigation) and Guest TDCALLs. + */ + err = tdh_mem_page_remove(&kvm_tdx->td, gpa, tdx_level, &entry, + &level_state); + + if (unlikely(tdx_operand_busy(err))) { + /* + * The second retry is expected to succeed after kicking off all + * other vCPUs and prevent them from invoking TDH.VP.ENTER. + */ + tdx_no_vcpus_enter_start(kvm); + err = tdh_mem_page_remove(&kvm_tdx->td, gpa, tdx_level, &entry, + &level_state); + tdx_no_vcpus_enter_stop(kvm); + } + + if (KVM_BUG_ON(err, kvm)) { + pr_tdx_error_2(TDH_MEM_PAGE_REMOVE, err, entry, level_state); + return -EIO; + } + + err = tdh_phymem_page_wbinvd_hkid((u16)kvm_tdx->hkid, page); + if (KVM_BUG_ON(err, kvm)) { + pr_tdx_error(TDH_PHYMEM_PAGE_WBINVD, err); + return -EIO; + } + + tdx_quirk_reset_page(page); + return 0; } void tdx_deliver_interrupt(struct kvm_lapic *apic, int delivery_mode, From 7139c860650535cf517a9344212ce56a21ba37f5 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:34 -0700 Subject: [PATCH 11/33] KVM: x86/mmu: Drop the return code from kvm_x86_ops.remove_external_spte() Drop the return code from kvm_x86_ops.remove_external_spte(), a.k.a. tdx_sept_remove_private_spte(), as KVM simply does a KVM_BUG_ON() failure, and that KVM_BUG_ON() is redundant since all error paths in TDX also do a KVM_BUG_ON(). Opportunistically pass the spte instead of the pfn, as the API is clearly about removing an spte. Suggested-by: Rick Edgecombe Reviewed-by: Binbin Wu Reviewed-by: Kai Huang Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-12-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/include/asm/kvm_host.h | 4 ++-- arch/x86/kvm/mmu/tdp_mmu.c | 8 ++------ arch/x86/kvm/vmx/tdx.c | 17 ++++++++--------- 3 files changed, 12 insertions(+), 17 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 48598d017d6f..b5867f8fe6ce 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1855,8 +1855,8 @@ struct kvm_x86_ops { void *external_spt); /* Update external page table from spte getting removed, and flush TLB. */ - int (*remove_external_spte)(struct kvm *kvm, gfn_t gfn, enum pg_level level, - kvm_pfn_t pfn_for_gfn); + void (*remove_external_spte)(struct kvm *kvm, gfn_t gfn, enum pg_level level, + u64 mirror_spte); bool (*has_wbinvd_exit)(void); diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index e735d2f8367b..e1a96e9ea1bb 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -362,9 +362,6 @@ static void tdp_mmu_unlink_sp(struct kvm *kvm, struct kvm_mmu_page *sp) static void remove_external_spte(struct kvm *kvm, gfn_t gfn, u64 old_spte, int level) { - kvm_pfn_t old_pfn = spte_to_pfn(old_spte); - int ret; - /* * External (TDX) SPTEs are limited to PG_LEVEL_4K, and external * PTs are removed in a special order, involving free_external_spt(). @@ -377,9 +374,8 @@ static void remove_external_spte(struct kvm *kvm, gfn_t gfn, u64 old_spte, /* Zapping leaf spte is allowed only when write lock is held. */ lockdep_assert_held_write(&kvm->mmu_lock); - /* Because write lock is held, operation should success. */ - ret = kvm_x86_call(remove_external_spte)(kvm, gfn, level, old_pfn); - KVM_BUG_ON(ret, kvm); + + kvm_x86_call(remove_external_spte)(kvm, gfn, level, old_spte); } /** diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 667cd089eec8..247c35164565 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -1806,12 +1806,12 @@ static int tdx_sept_free_private_spt(struct kvm *kvm, gfn_t gfn, return tdx_reclaim_page(virt_to_page(private_spt)); } -static int tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn, - enum pg_level level, kvm_pfn_t pfn) +static void tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn, + enum pg_level level, u64 mirror_spte) { + struct page *page = pfn_to_page(spte_to_pfn(mirror_spte)); int tdx_level = pg_level_to_tdx_sept_level(level); struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm); - struct page *page = pfn_to_page(pfn); gpa_t gpa = gfn_to_gpa(gfn); u64 err, entry, level_state; int ret; @@ -1822,15 +1822,15 @@ static int tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn, * there can't be anything populated in the private EPT. */ if (KVM_BUG_ON(!is_hkid_assigned(to_kvm_tdx(kvm)), kvm)) - return -EIO; + return; /* TODO: handle large pages. */ if (KVM_BUG_ON(level != PG_LEVEL_4K, kvm)) - return -EIO; + return; ret = tdx_sept_zap_private_spte(kvm, gfn, level, page); if (ret <= 0) - return ret; + return; /* * TDX requires TLB tracking before dropping private page. Do @@ -1859,17 +1859,16 @@ static int tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn, if (KVM_BUG_ON(err, kvm)) { pr_tdx_error_2(TDH_MEM_PAGE_REMOVE, err, entry, level_state); - return -EIO; + return; } err = tdh_phymem_page_wbinvd_hkid((u16)kvm_tdx->hkid, page); if (KVM_BUG_ON(err, kvm)) { pr_tdx_error(TDH_PHYMEM_PAGE_WBINVD, err); - return -EIO; + return; } tdx_quirk_reset_page(page); - return 0; } void tdx_deliver_interrupt(struct kvm_lapic *apic, int delivery_mode, From b9d5cf6de0b6bd3bdd8957b5fea5a243e43c928f Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:35 -0700 Subject: [PATCH 12/33] KVM: TDX: WARN if mirror SPTE doesn't have full RWX when creating S-EPT mapping Pass in the mirror_spte to kvm_x86_ops.set_external_spte() to provide symmetry with .remove_external_spte(), and assert in TDX that the mirror SPTE is shadow-present with full RWX permissions (the TDX-Module doesn't allow the hypervisor to control protections). Reviewed-by: Binbin Wu Reviewed-by: Kai Huang Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-13-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/include/asm/kvm_host.h | 2 +- arch/x86/kvm/mmu/tdp_mmu.c | 3 +-- arch/x86/kvm/vmx/tdx.c | 6 +++++- 3 files changed, 7 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index b5867f8fe6ce..87a5f5100b1d 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1848,7 +1848,7 @@ struct kvm_x86_ops { void *external_spt); /* Update the external page table from spte getting set. */ int (*set_external_spte)(struct kvm *kvm, gfn_t gfn, enum pg_level level, - kvm_pfn_t pfn_for_gfn); + u64 mirror_spte); /* Update external page tables for page table about to be freed. */ int (*free_external_spt)(struct kvm *kvm, gfn_t gfn, enum pg_level level, diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index e1a96e9ea1bb..9c26038f6b77 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -515,7 +515,6 @@ static int __must_check set_external_spte_present(struct kvm *kvm, tdp_ptep_t sp bool was_present = is_shadow_present_pte(old_spte); bool is_present = is_shadow_present_pte(new_spte); bool is_leaf = is_present && is_last_spte(new_spte, level); - kvm_pfn_t new_pfn = spte_to_pfn(new_spte); int ret = 0; KVM_BUG_ON(was_present, kvm); @@ -534,7 +533,7 @@ static int __must_check set_external_spte_present(struct kvm *kvm, tdp_ptep_t sp * external page table, or leaf. */ if (is_leaf) { - ret = kvm_x86_call(set_external_spte)(kvm, gfn, level, new_pfn); + ret = kvm_x86_call(set_external_spte)(kvm, gfn, level, new_spte); } else { void *external_spt = get_external_spt(gfn, new_spte, level); diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 247c35164565..1315fd9fdd6e 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -1629,14 +1629,18 @@ static int tdx_mem_page_record_premap_cnt(struct kvm *kvm, gfn_t gfn, } static int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn, - enum pg_level level, kvm_pfn_t pfn) + enum pg_level level, u64 mirror_spte) { struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm); + kvm_pfn_t pfn = spte_to_pfn(mirror_spte); /* TODO: handle large pages. */ if (KVM_BUG_ON(level != PG_LEVEL_4K, kvm)) return -EIO; + WARN_ON_ONCE(!is_shadow_present_pte(mirror_spte) || + (mirror_spte & VMX_EPT_RWX_MASK) != VMX_EPT_RWX_MASK); + /* * Read 'pre_fault_allowed' before 'kvm_tdx->state'; see matching * barrier in tdx_td_finalize(). From 24adff39705223f06607926f2717e6f8dec12d28 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:36 -0700 Subject: [PATCH 13/33] KVM: TDX: Avoid a double-KVM_BUG_ON() in tdx_sept_zap_private_spte() Return -EIO immediately from tdx_sept_zap_private_spte() if the number of to-be-added pages underflows, so that the following "KVM_BUG_ON(err, kvm)" isn't also triggered. Isolating the check from the "is premap error" if-statement will also allow adding a lockdep assertion that premap errors are encountered if and only if slots_lock is held. Reviewed-by: Rick Edgecombe Reviewed-by: Binbin Wu Reviewed-by: Kai Huang Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-14-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 1315fd9fdd6e..4426146d403e 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -1725,8 +1725,10 @@ static int tdx_sept_zap_private_spte(struct kvm *kvm, gfn_t gfn, err = tdh_mem_range_block(&kvm_tdx->td, gpa, tdx_level, &entry, &level_state); tdx_no_vcpus_enter_stop(kvm); } - if (tdx_is_sept_zap_err_due_to_premap(kvm_tdx, err, entry, level) && - !KVM_BUG_ON(!atomic64_read(&kvm_tdx->nr_premapped), kvm)) { + if (tdx_is_sept_zap_err_due_to_premap(kvm_tdx, err, entry, level)) { + if (KVM_BUG_ON(!atomic64_read(&kvm_tdx->nr_premapped), kvm)) + return -EIO; + atomic64_dec(&kvm_tdx->nr_premapped); return 0; } From af96d5452e5e88019bed9c081d4be1c489d7c081 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:37 -0700 Subject: [PATCH 14/33] KVM: TDX: Use atomic64_dec_return() instead of a poor equivalent Use atomic64_dec_return() when decrementing the number of "pre-mapped" S-EPT pages to ensure that the count can't go negative without KVM noticing. In theory, checking for '0' and then decrementing in a separate operation could miss a 0=>-1 transition. In practice, such a condition is impossible because nr_premapped is protected by slots_lock, i.e. doesn't actually need to be an atomic (that wart will be addressed shortly). Don't bother trying to keep the count non-negative, as the KVM_BUG_ON() ensures the VM is dead, i.e. there's no point in trying to limp along. Reviewed-by: Rick Edgecombe Reviewed-by: Ira Weiny Reviewed-by: Binbin Wu Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-15-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 4426146d403e..8482eadbbb8f 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -1726,10 +1726,9 @@ static int tdx_sept_zap_private_spte(struct kvm *kvm, gfn_t gfn, tdx_no_vcpus_enter_stop(kvm); } if (tdx_is_sept_zap_err_due_to_premap(kvm_tdx, err, entry, level)) { - if (KVM_BUG_ON(!atomic64_read(&kvm_tdx->nr_premapped), kvm)) + if (KVM_BUG_ON(atomic64_dec_return(&kvm_tdx->nr_premapped) < 0, kvm)) return -EIO; - atomic64_dec(&kvm_tdx->nr_premapped); return 0; } @@ -3171,8 +3170,7 @@ static int tdx_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, goto out; } - if (!KVM_BUG_ON(!atomic64_read(&kvm_tdx->nr_premapped), kvm)) - atomic64_dec(&kvm_tdx->nr_premapped); + KVM_BUG_ON(atomic64_dec_return(&kvm_tdx->nr_premapped) < 0, kvm); if (arg->flags & KVM_TDX_MEASURE_MEMORY_REGION) { for (i = 0; i < PAGE_SIZE; i += TDX_EXTENDMR_CHUNKSIZE) { From b4b2b6eda5afa92f42fd1cd67f2729acf7e95f5b Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:38 -0700 Subject: [PATCH 15/33] KVM: TDX: Fold tdx_mem_page_record_premap_cnt() into its sole caller Fold tdx_mem_page_record_premap_cnt() into tdx_sept_set_private_spte() as providing a one-off helper for effectively three lines of code is at best a wash, and splitting the code makes the comment for smp_rmb() _extremely_ confusing as the comment talks about reading kvm->arch.pre_fault_allowed before kvm_tdx->state, but the immediately visible code does the exact opposite. Opportunistically rewrite the comments to more explicitly explain who is checking what, as well as _why_ the ordering matters. No functional change intended. Reviewed-by: Rick Edgecombe Reviewed-by: Binbin Wu Reviewed-by: Kai Huang Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-16-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 49 ++++++++++++++++++------------------------ 1 file changed, 21 insertions(+), 28 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 8482eadbbb8f..addd3678d03d 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -1605,29 +1605,6 @@ static int tdx_mem_page_aug(struct kvm *kvm, gfn_t gfn, return 0; } -/* - * KVM_TDX_INIT_MEM_REGION calls kvm_gmem_populate() to map guest pages; the - * callback tdx_gmem_post_populate() then maps pages into private memory. - * through the a seamcall TDH.MEM.PAGE.ADD(). The SEAMCALL also requires the - * private EPT structures for the page to have been built before, which is - * done via kvm_tdp_map_page(). nr_premapped counts the number of pages that - * were added to the EPT structures but not added with TDH.MEM.PAGE.ADD(). - * The counter has to be zero on KVM_TDX_FINALIZE_VM, to ensure that there - * are no half-initialized shared EPT pages. - */ -static int tdx_mem_page_record_premap_cnt(struct kvm *kvm, gfn_t gfn, - enum pg_level level, kvm_pfn_t pfn) -{ - struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm); - - if (KVM_BUG_ON(kvm->arch.pre_fault_allowed, kvm)) - return -EIO; - - /* nr_premapped will be decreased when tdh_mem_page_add() is called. */ - atomic64_inc(&kvm_tdx->nr_premapped); - return 0; -} - static int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn, enum pg_level level, u64 mirror_spte) { @@ -1642,14 +1619,30 @@ static int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn, (mirror_spte & VMX_EPT_RWX_MASK) != VMX_EPT_RWX_MASK); /* - * Read 'pre_fault_allowed' before 'kvm_tdx->state'; see matching - * barrier in tdx_td_finalize(). + * Ensure pre_fault_allowed is read by kvm_arch_vcpu_pre_fault_memory() + * before kvm_tdx->state. Userspace must not be allowed to pre-fault + * arbitrary memory until the initial memory image is finalized. Pairs + * with the smp_wmb() in tdx_td_finalize(). */ smp_rmb(); - if (likely(kvm_tdx->state == TD_STATE_RUNNABLE)) - return tdx_mem_page_aug(kvm, gfn, level, pfn); - return tdx_mem_page_record_premap_cnt(kvm, gfn, level, pfn); + /* + * If the TD isn't finalized/runnable, then userspace is initializing + * the VM image via KVM_TDX_INIT_MEM_REGION. Increment the number of + * pages that need to be mapped and initialized via TDH.MEM.PAGE.ADD. + * KVM_TDX_FINALIZE_VM checks the counter to ensure all pre-mapped + * pages have been added to the image, to prevent running the TD with a + * valid mapping in the mirror EPT, but not in the S-EPT. + */ + if (unlikely(kvm_tdx->state != TD_STATE_RUNNABLE)) { + if (KVM_BUG_ON(kvm->arch.pre_fault_allowed, kvm)) + return -EIO; + + atomic64_inc(&kvm_tdx->nr_premapped); + return 0; + } + + return tdx_mem_page_aug(kvm, gfn, level, pfn); } static int tdx_sept_link_private_spt(struct kvm *kvm, gfn_t gfn, From 6b5b71ffabf9b0eb250ae6d4e0ab7fbac622f0f0 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:39 -0700 Subject: [PATCH 16/33] KVM: TDX: ADD pages to the TD image while populating mirror EPT entries When populating the initial memory image for a TDX guest, ADD pages to the TD as part of establishing the mappings in the mirror EPT, as opposed to creating the mappings and then doing ADD after the fact. Doing ADD in the S-EPT callbacks eliminates the need to track "premapped" pages, as the mirror EPT (M-EPT) and S-EPT are always synchronized, e.g. if ADD fails, KVM reverts to the previous M-EPT entry (guaranteed to be !PRESENT). Eliminating the hole where the M-EPT can have a mapping that doesn't exist in the S-EPT in turn obviates the need to handle errors that are unique to encountering a missing S-EPT entry (see tdx_is_sept_zap_err_due_to_premap()). Keeping the M-EPT and S-EPT synchronized also eliminates the need to check for unconsumed "premap" entries during tdx_td_finalize(), as there simply can't be any such entries. Dropping that check in particular reduces the overall cognitive load, as the management of nr_premapped with respect to removal of S-EPT is _very_ subtle. E.g. successful removal of an S-EPT entry after it completed ADD doesn't adjust nr_premapped, but it's not clear why that's "ok" but having half-baked entries is not (it's not truly "ok" in that removing pages from the image will likely prevent the guest from booting, but from KVM's perspective it's "ok"). Doing ADD in the S-EPT path requires passing an argument via a scratch field, but the current approach of tracking the number of "premapped" pages effectively does the same. And the "premapped" counter is much more dangerous, as it doesn't have a singular lock to protect its usage, since nr_premapped can be modified as soon as mmu_lock is dropped, at least in theory. I.e. nr_premapped is guarded by slots_lock, but only for "happy" paths. Note, this approach was used/tried at various points in TDX development, but was ultimately discarded due to a desire to avoid stashing temporary state in kvm_tdx. But as above, KVM ended up with such state anyways, and fully committing to using temporary state provides better access rules (100% guarded by slots_lock), and makes several edge cases flat out impossible. Note #2, continue to extend the measurement outside of mmu_lock, as it's a slow operation (typically 16 SEAMCALLs per page whose data is included in the measurement), and doesn't *need* to be done under mmu_lock, e.g. for consistency purposes. However, MR.EXTEND isn't _that_ slow, e.g. ~1ms latency to measure a full page, so if it needs to be done under mmu_lock in the future, e.g. because KVM gains a flow that can remove S-EPT entries during KVM_TDX_INIT_MEM_REGION, then extending the measurement can also be moved into the S-EPT mapping path (again, only if absolutely necessary). P.S. _If_ MR.EXTEND is moved into the S-EPT path, take care not to return an error up the stack if TDH_MR_EXTEND fails, as removing the M-EPT entry but not the S-EPT entry would result in inconsistent state! Reviewed-by: Rick Edgecombe Reviewed-by: Kai Huang Reviewed-by: Binbin Wu Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-17-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 106 ++++++++++++++--------------------------- arch/x86/kvm/vmx/tdx.h | 8 +++- 2 files changed, 43 insertions(+), 71 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index addd3678d03d..14cadd0d71c0 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -1583,6 +1583,32 @@ void tdx_load_mmu_pgd(struct kvm_vcpu *vcpu, hpa_t root_hpa, int pgd_level) td_vmcs_write64(to_tdx(vcpu), SHARED_EPT_POINTER, root_hpa); } +static int tdx_mem_page_add(struct kvm *kvm, gfn_t gfn, enum pg_level level, + kvm_pfn_t pfn) +{ + struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm); + u64 err, entry, level_state; + gpa_t gpa = gfn_to_gpa(gfn); + + lockdep_assert_held(&kvm->slots_lock); + + if (KVM_BUG_ON(kvm->arch.pre_fault_allowed, kvm) || + KVM_BUG_ON(!kvm_tdx->page_add_src, kvm)) + return -EIO; + + err = tdh_mem_page_add(&kvm_tdx->td, gpa, pfn_to_page(pfn), + kvm_tdx->page_add_src, &entry, &level_state); + if (unlikely(tdx_operand_busy(err))) + return -EBUSY; + + if (KVM_BUG_ON(err, kvm)) { + pr_tdx_error_2(TDH_MEM_PAGE_ADD, err, entry, level_state); + return -EIO; + } + + return 0; +} + static int tdx_mem_page_aug(struct kvm *kvm, gfn_t gfn, enum pg_level level, kvm_pfn_t pfn) { @@ -1628,19 +1654,10 @@ static int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn, /* * If the TD isn't finalized/runnable, then userspace is initializing - * the VM image via KVM_TDX_INIT_MEM_REGION. Increment the number of - * pages that need to be mapped and initialized via TDH.MEM.PAGE.ADD. - * KVM_TDX_FINALIZE_VM checks the counter to ensure all pre-mapped - * pages have been added to the image, to prevent running the TD with a - * valid mapping in the mirror EPT, but not in the S-EPT. + * the VM image via KVM_TDX_INIT_MEM_REGION; ADD the page to the TD. */ - if (unlikely(kvm_tdx->state != TD_STATE_RUNNABLE)) { - if (KVM_BUG_ON(kvm->arch.pre_fault_allowed, kvm)) - return -EIO; - - atomic64_inc(&kvm_tdx->nr_premapped); - return 0; - } + if (unlikely(kvm_tdx->state != TD_STATE_RUNNABLE)) + return tdx_mem_page_add(kvm, gfn, level, pfn); return tdx_mem_page_aug(kvm, gfn, level, pfn); } @@ -1666,39 +1683,6 @@ static int tdx_sept_link_private_spt(struct kvm *kvm, gfn_t gfn, return 0; } -/* - * Check if the error returned from a SEPT zap SEAMCALL is due to that a page is - * mapped by KVM_TDX_INIT_MEM_REGION without tdh_mem_page_add() being called - * successfully. - * - * Since tdh_mem_sept_add() must have been invoked successfully before a - * non-leaf entry present in the mirrored page table, the SEPT ZAP related - * SEAMCALLs should not encounter err TDX_EPT_WALK_FAILED. They should instead - * find TDX_EPT_ENTRY_STATE_INCORRECT due to an empty leaf entry found in the - * SEPT. - * - * Further check if the returned entry from SEPT walking is with RWX permissions - * to filter out anything unexpected. - * - * Note: @level is pg_level, not the tdx_level. The tdx_level extracted from - * level_state returned from a SEAMCALL error is the same as that passed into - * the SEAMCALL. - */ -static int tdx_is_sept_zap_err_due_to_premap(struct kvm_tdx *kvm_tdx, u64 err, - u64 entry, int level) -{ - if (!err || kvm_tdx->state == TD_STATE_RUNNABLE) - return false; - - if (err != (TDX_EPT_ENTRY_STATE_INCORRECT | TDX_OPERAND_ID_RCX)) - return false; - - if ((is_last_spte(entry, level) && (entry & VMX_EPT_RWX_MASK))) - return false; - - return true; -} - static int tdx_sept_zap_private_spte(struct kvm *kvm, gfn_t gfn, enum pg_level level, struct page *page) { @@ -1718,12 +1702,6 @@ static int tdx_sept_zap_private_spte(struct kvm *kvm, gfn_t gfn, err = tdh_mem_range_block(&kvm_tdx->td, gpa, tdx_level, &entry, &level_state); tdx_no_vcpus_enter_stop(kvm); } - if (tdx_is_sept_zap_err_due_to_premap(kvm_tdx, err, entry, level)) { - if (KVM_BUG_ON(atomic64_dec_return(&kvm_tdx->nr_premapped) < 0, kvm)) - return -EIO; - - return 0; - } if (KVM_BUG_ON(err, kvm)) { pr_tdx_error_2(TDH_MEM_RANGE_BLOCK, err, entry, level_state); @@ -2839,12 +2817,6 @@ static int tdx_td_finalize(struct kvm *kvm, struct kvm_tdx_cmd *cmd) if (!is_hkid_assigned(kvm_tdx) || kvm_tdx->state == TD_STATE_RUNNABLE) return -EINVAL; - /* - * Pages are pending for KVM_TDX_INIT_MEM_REGION to issue - * TDH.MEM.PAGE.ADD(). - */ - if (atomic64_read(&kvm_tdx->nr_premapped)) - return -EINVAL; cmd->hw_error = tdh_mr_finalize(&kvm_tdx->td); if (tdx_operand_busy(cmd->hw_error)) @@ -3141,6 +3113,9 @@ static int tdx_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, struct page *src_page; int ret, i; + if (KVM_BUG_ON(kvm_tdx->page_add_src, kvm)) + return -EIO; + /* * Get the source page if it has been faulted in. Return failure if the * source page has been swapped out or unmapped in primary memory. @@ -3151,19 +3126,14 @@ static int tdx_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, if (ret != 1) return -ENOMEM; + kvm_tdx->page_add_src = src_page; ret = kvm_tdp_mmu_map_private_pfn(arg->vcpu, gfn, pfn); - if (ret < 0) - goto out; + kvm_tdx->page_add_src = NULL; - ret = 0; - err = tdh_mem_page_add(&kvm_tdx->td, gpa, pfn_to_page(pfn), - src_page, &entry, &level_state); - if (err) { - ret = unlikely(tdx_operand_busy(err)) ? -EBUSY : -EIO; - goto out; - } + put_page(src_page); - KVM_BUG_ON(atomic64_dec_return(&kvm_tdx->nr_premapped) < 0, kvm); + if (ret) + return ret; if (arg->flags & KVM_TDX_MEASURE_MEMORY_REGION) { for (i = 0; i < PAGE_SIZE; i += TDX_EXTENDMR_CHUNKSIZE) { @@ -3176,8 +3146,6 @@ static int tdx_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, } } -out: - put_page(src_page); return ret; } diff --git a/arch/x86/kvm/vmx/tdx.h b/arch/x86/kvm/vmx/tdx.h index ca39a9391db1..1239d9845093 100644 --- a/arch/x86/kvm/vmx/tdx.h +++ b/arch/x86/kvm/vmx/tdx.h @@ -36,8 +36,12 @@ struct kvm_tdx { struct tdx_td td; - /* For KVM_TDX_INIT_MEM_REGION. */ - atomic64_t nr_premapped; + /* + * Scratch pointer used to pass the source page to tdx_mem_page_add(). + * Protected by slots_lock, and non-NULL only when mapping a private + * pfn via tdx_gmem_post_populate(). + */ + struct page *page_add_src; /* * Prevent vCPUs from TD entry to ensure SEPT zap related SEAMCALLs do From 14c9938619bee7743eb2f2443b7d5f412a80838b Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:40 -0700 Subject: [PATCH 17/33] KVM: TDX: Fold tdx_sept_zap_private_spte() into tdx_sept_remove_private_spte() Do TDH_MEM_RANGE_BLOCK directly in tdx_sept_remove_private_spte() instead of using a one-off helper now that the nr_premapped tracking is gone. Opportunistically drop the WARN on hugepages, which was dead code (see the KVM_BUG_ON() in tdx_sept_remove_private_spte()). No functional change intended. Reviewed-by: Rick Edgecombe Reviewed-by: Kai Huang Reviewed-by: Binbin Wu Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-18-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 41 +++++++++++------------------------------ 1 file changed, 11 insertions(+), 30 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 14cadd0d71c0..797771918b2a 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -1683,33 +1683,6 @@ static int tdx_sept_link_private_spt(struct kvm *kvm, gfn_t gfn, return 0; } -static int tdx_sept_zap_private_spte(struct kvm *kvm, gfn_t gfn, - enum pg_level level, struct page *page) -{ - int tdx_level = pg_level_to_tdx_sept_level(level); - struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm); - gpa_t gpa = gfn_to_gpa(gfn) & KVM_HPAGE_MASK(level); - u64 err, entry, level_state; - - /* For now large page isn't supported yet. */ - WARN_ON_ONCE(level != PG_LEVEL_4K); - - err = tdh_mem_range_block(&kvm_tdx->td, gpa, tdx_level, &entry, &level_state); - - if (unlikely(tdx_operand_busy(err))) { - /* After no vCPUs enter, the second retry is expected to succeed */ - tdx_no_vcpus_enter_start(kvm); - err = tdh_mem_range_block(&kvm_tdx->td, gpa, tdx_level, &entry, &level_state); - tdx_no_vcpus_enter_stop(kvm); - } - - if (KVM_BUG_ON(err, kvm)) { - pr_tdx_error_2(TDH_MEM_RANGE_BLOCK, err, entry, level_state); - return -EIO; - } - return 1; -} - /* * Ensure shared and private EPTs to be flushed on all vCPUs. * tdh_mem_track() is the only caller that increases TD epoch. An increase in @@ -1790,7 +1763,6 @@ static void tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn, struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm); gpa_t gpa = gfn_to_gpa(gfn); u64 err, entry, level_state; - int ret; /* * HKID is released after all private pages have been removed, and set @@ -1804,9 +1776,18 @@ static void tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn, if (KVM_BUG_ON(level != PG_LEVEL_4K, kvm)) return; - ret = tdx_sept_zap_private_spte(kvm, gfn, level, page); - if (ret <= 0) + err = tdh_mem_range_block(&kvm_tdx->td, gpa, tdx_level, &entry, &level_state); + if (unlikely(tdx_operand_busy(err))) { + /* After no vCPUs enter, the second retry is expected to succeed */ + tdx_no_vcpus_enter_start(kvm); + err = tdh_mem_range_block(&kvm_tdx->td, gpa, tdx_level, &entry, &level_state); + tdx_no_vcpus_enter_stop(kvm); + } + + if (KVM_BUG_ON(err, kvm)) { + pr_tdx_error_2(TDH_MEM_RANGE_BLOCK, err, entry, level_state); return; + } /* * TDX requires TLB tracking before dropping private page. Do From 597d7068702fc3120b6a37bb8c5cd6c1bab898e0 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:41 -0700 Subject: [PATCH 18/33] KVM: TDX: Combine KVM_BUG_ON + pr_tdx_error() into TDX_BUG_ON() Add TDX_BUG_ON() macros (with varying numbers of arguments) to deduplicate the myriad flows that do KVM_BUG_ON()/WARN_ON_ONCE() followed by a call to pr_tdx_error(). In addition to reducing boilerplate copy+paste code, this also helps ensure that KVM provides consistent handling of SEAMCALL errors. Opportunistically convert a handful of bare WARN_ON_ONCE() paths to the equivalent of KVM_BUG_ON(), i.e. have them terminate the VM. If a SEAMCALL error is fatal enough to WARN on, it's fatal enough to terminate the TD. Reviewed-by: Rick Edgecombe Reviewed-by: Binbin Wu Reviewed-by: Kai Huang Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-19-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 110 +++++++++++++++++------------------------ 1 file changed, 46 insertions(+), 64 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 797771918b2a..5a30d77375cc 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -24,20 +24,32 @@ #undef pr_fmt #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt -#define pr_tdx_error(__fn, __err) \ - pr_err_ratelimited("SEAMCALL %s failed: 0x%llx\n", #__fn, __err) +#define __TDX_BUG_ON(__err, __f, __kvm, __fmt, __args...) \ +({ \ + struct kvm *_kvm = (__kvm); \ + bool __ret = !!(__err); \ + \ + if (WARN_ON_ONCE(__ret && (!_kvm || !_kvm->vm_bugged))) { \ + if (_kvm) \ + kvm_vm_bugged(_kvm); \ + pr_err_ratelimited("SEAMCALL " __f " failed: 0x%llx" __fmt "\n",\ + __err, __args); \ + } \ + unlikely(__ret); \ +}) -#define __pr_tdx_error_N(__fn_str, __err, __fmt, ...) \ - pr_err_ratelimited("SEAMCALL " __fn_str " failed: 0x%llx, " __fmt, __err, __VA_ARGS__) +#define TDX_BUG_ON(__err, __fn, __kvm) \ + __TDX_BUG_ON(__err, #__fn, __kvm, "%s", "") -#define pr_tdx_error_1(__fn, __err, __rcx) \ - __pr_tdx_error_N(#__fn, __err, "rcx 0x%llx\n", __rcx) +#define TDX_BUG_ON_1(__err, __fn, __rcx, __kvm) \ + __TDX_BUG_ON(__err, #__fn, __kvm, ", rcx 0x%llx", __rcx) -#define pr_tdx_error_2(__fn, __err, __rcx, __rdx) \ - __pr_tdx_error_N(#__fn, __err, "rcx 0x%llx, rdx 0x%llx\n", __rcx, __rdx) +#define TDX_BUG_ON_2(__err, __fn, __rcx, __rdx, __kvm) \ + __TDX_BUG_ON(__err, #__fn, __kvm, ", rcx 0x%llx, rdx 0x%llx", __rcx, __rdx) + +#define TDX_BUG_ON_3(__err, __fn, __rcx, __rdx, __r8, __kvm) \ + __TDX_BUG_ON(__err, #__fn, __kvm, ", rcx 0x%llx, rdx 0x%llx, r8 0x%llx", __rcx, __rdx, __r8) -#define pr_tdx_error_3(__fn, __err, __rcx, __rdx, __r8) \ - __pr_tdx_error_N(#__fn, __err, "rcx 0x%llx, rdx 0x%llx, r8 0x%llx\n", __rcx, __rdx, __r8) bool enable_tdx __ro_after_init; module_param_named(tdx, enable_tdx, bool, 0444); @@ -313,10 +325,9 @@ static int __tdx_reclaim_page(struct page *page) * before the HKID is released and control pages have also been * released at this point, so there is no possibility of contention. */ - if (WARN_ON_ONCE(err)) { - pr_tdx_error_3(TDH_PHYMEM_PAGE_RECLAIM, err, rcx, rdx, r8); + if (TDX_BUG_ON_3(err, TDH_PHYMEM_PAGE_RECLAIM, rcx, rdx, r8, NULL)) return -EIO; - } + return 0; } @@ -404,8 +415,8 @@ static void tdx_flush_vp_on_cpu(struct kvm_vcpu *vcpu) return; smp_call_function_single(cpu, tdx_flush_vp, &arg, 1); - if (KVM_BUG_ON(arg.err, vcpu->kvm)) - pr_tdx_error(TDH_VP_FLUSH, arg.err); + + TDX_BUG_ON(arg.err, TDH_VP_FLUSH, vcpu->kvm); } void tdx_disable_virtualization_cpu(void) @@ -464,8 +475,7 @@ static void smp_func_do_phymem_cache_wb(void *unused) } out: - if (WARN_ON_ONCE(err)) - pr_tdx_error(TDH_PHYMEM_CACHE_WB, err); + TDX_BUG_ON(err, TDH_PHYMEM_CACHE_WB, NULL); } void tdx_mmu_release_hkid(struct kvm *kvm) @@ -504,8 +514,7 @@ void tdx_mmu_release_hkid(struct kvm *kvm) err = tdh_mng_vpflushdone(&kvm_tdx->td); if (err == TDX_FLUSHVP_NOT_DONE) goto out; - if (KVM_BUG_ON(err, kvm)) { - pr_tdx_error(TDH_MNG_VPFLUSHDONE, err); + if (TDX_BUG_ON(err, TDH_MNG_VPFLUSHDONE, kvm)) { pr_err("tdh_mng_vpflushdone() failed. HKID %d is leaked.\n", kvm_tdx->hkid); goto out; @@ -528,8 +537,7 @@ void tdx_mmu_release_hkid(struct kvm *kvm) * tdh_mng_key_freeid() will fail. */ err = tdh_mng_key_freeid(&kvm_tdx->td); - if (KVM_BUG_ON(err, kvm)) { - pr_tdx_error(TDH_MNG_KEY_FREEID, err); + if (TDX_BUG_ON(err, TDH_MNG_KEY_FREEID, kvm)) { pr_err("tdh_mng_key_freeid() failed. HKID %d is leaked.\n", kvm_tdx->hkid); } else { @@ -580,10 +588,9 @@ static void tdx_reclaim_td_control_pages(struct kvm *kvm) * when it is reclaiming TDCS). */ err = tdh_phymem_page_wbinvd_tdr(&kvm_tdx->td); - if (KVM_BUG_ON(err, kvm)) { - pr_tdx_error(TDH_PHYMEM_PAGE_WBINVD, err); + if (TDX_BUG_ON(err, TDH_PHYMEM_PAGE_WBINVD, kvm)) return; - } + tdx_quirk_reset_page(kvm_tdx->td.tdr_page); __free_page(kvm_tdx->td.tdr_page); @@ -606,11 +613,8 @@ static int tdx_do_tdh_mng_key_config(void *param) /* TDX_RND_NO_ENTROPY related retries are handled by sc_retry() */ err = tdh_mng_key_config(&kvm_tdx->td); - - if (KVM_BUG_ON(err, &kvm_tdx->kvm)) { - pr_tdx_error(TDH_MNG_KEY_CONFIG, err); + if (TDX_BUG_ON(err, TDH_MNG_KEY_CONFIG, &kvm_tdx->kvm)) return -EIO; - } return 0; } @@ -1601,10 +1605,8 @@ static int tdx_mem_page_add(struct kvm *kvm, gfn_t gfn, enum pg_level level, if (unlikely(tdx_operand_busy(err))) return -EBUSY; - if (KVM_BUG_ON(err, kvm)) { - pr_tdx_error_2(TDH_MEM_PAGE_ADD, err, entry, level_state); + if (TDX_BUG_ON_2(err, TDH_MEM_PAGE_ADD, entry, level_state, kvm)) return -EIO; - } return 0; } @@ -1623,10 +1625,8 @@ static int tdx_mem_page_aug(struct kvm *kvm, gfn_t gfn, if (unlikely(tdx_operand_busy(err))) return -EBUSY; - if (KVM_BUG_ON(err, kvm)) { - pr_tdx_error_2(TDH_MEM_PAGE_AUG, err, entry, level_state); + if (TDX_BUG_ON_2(err, TDH_MEM_PAGE_AUG, entry, level_state, kvm)) return -EIO; - } return 0; } @@ -1675,10 +1675,8 @@ static int tdx_sept_link_private_spt(struct kvm *kvm, gfn_t gfn, if (unlikely(tdx_operand_busy(err))) return -EBUSY; - if (KVM_BUG_ON(err, kvm)) { - pr_tdx_error_2(TDH_MEM_SEPT_ADD, err, entry, level_state); + if (TDX_BUG_ON_2(err, TDH_MEM_SEPT_ADD, entry, level_state, kvm)) return -EIO; - } return 0; } @@ -1726,8 +1724,7 @@ static void tdx_track(struct kvm *kvm) tdx_no_vcpus_enter_stop(kvm); } - if (KVM_BUG_ON(err, kvm)) - pr_tdx_error(TDH_MEM_TRACK, err); + TDX_BUG_ON(err, TDH_MEM_TRACK, kvm); kvm_make_all_cpus_request(kvm, KVM_REQ_OUTSIDE_GUEST_MODE); } @@ -1784,10 +1781,8 @@ static void tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn, tdx_no_vcpus_enter_stop(kvm); } - if (KVM_BUG_ON(err, kvm)) { - pr_tdx_error_2(TDH_MEM_RANGE_BLOCK, err, entry, level_state); + if (TDX_BUG_ON_2(err, TDH_MEM_RANGE_BLOCK, entry, level_state, kvm)) return; - } /* * TDX requires TLB tracking before dropping private page. Do @@ -1814,16 +1809,12 @@ static void tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn, tdx_no_vcpus_enter_stop(kvm); } - if (KVM_BUG_ON(err, kvm)) { - pr_tdx_error_2(TDH_MEM_PAGE_REMOVE, err, entry, level_state); + if (TDX_BUG_ON_2(err, TDH_MEM_PAGE_REMOVE, entry, level_state, kvm)) return; - } err = tdh_phymem_page_wbinvd_hkid((u16)kvm_tdx->hkid, page); - if (KVM_BUG_ON(err, kvm)) { - pr_tdx_error(TDH_PHYMEM_PAGE_WBINVD, err); + if (TDX_BUG_ON(err, TDH_PHYMEM_PAGE_WBINVD, kvm)) return; - } tdx_quirk_reset_page(page); } @@ -2463,8 +2454,7 @@ static int __tdx_td_init(struct kvm *kvm, struct td_params *td_params, goto free_packages; } - if (WARN_ON_ONCE(err)) { - pr_tdx_error(TDH_MNG_CREATE, err); + if (TDX_BUG_ON(err, TDH_MNG_CREATE, kvm)) { ret = -EIO; goto free_packages; } @@ -2505,8 +2495,7 @@ static int __tdx_td_init(struct kvm *kvm, struct td_params *td_params, ret = -EAGAIN; goto teardown; } - if (WARN_ON_ONCE(err)) { - pr_tdx_error(TDH_MNG_ADDCX, err); + if (TDX_BUG_ON(err, TDH_MNG_ADDCX, kvm)) { ret = -EIO; goto teardown; } @@ -2523,8 +2512,7 @@ static int __tdx_td_init(struct kvm *kvm, struct td_params *td_params, *seamcall_err = err; ret = -EINVAL; goto teardown; - } else if (WARN_ON_ONCE(err)) { - pr_tdx_error_1(TDH_MNG_INIT, err, rcx); + } else if (TDX_BUG_ON_1(err, TDH_MNG_INIT, rcx, kvm)) { ret = -EIO; goto teardown; } @@ -2802,10 +2790,8 @@ static int tdx_td_finalize(struct kvm *kvm, struct kvm_tdx_cmd *cmd) cmd->hw_error = tdh_mr_finalize(&kvm_tdx->td); if (tdx_operand_busy(cmd->hw_error)) return -EBUSY; - if (KVM_BUG_ON(cmd->hw_error, kvm)) { - pr_tdx_error(TDH_MR_FINALIZE, cmd->hw_error); + if (TDX_BUG_ON(cmd->hw_error, TDH_MR_FINALIZE, kvm)) return -EIO; - } kvm_tdx->state = TD_STATE_RUNNABLE; /* TD_STATE_RUNNABLE must be set before 'pre_fault_allowed' */ @@ -2892,16 +2878,14 @@ static int tdx_td_vcpu_init(struct kvm_vcpu *vcpu, u64 vcpu_rcx) } err = tdh_vp_create(&kvm_tdx->td, &tdx->vp); - if (KVM_BUG_ON(err, vcpu->kvm)) { + if (TDX_BUG_ON(err, TDH_VP_CREATE, vcpu->kvm)) { ret = -EIO; - pr_tdx_error(TDH_VP_CREATE, err); goto free_tdcx; } for (i = 0; i < kvm_tdx->td.tdcx_nr_pages; i++) { err = tdh_vp_addcx(&tdx->vp, tdx->vp.tdcx_pages[i]); - if (KVM_BUG_ON(err, vcpu->kvm)) { - pr_tdx_error(TDH_VP_ADDCX, err); + if (TDX_BUG_ON(err, TDH_VP_ADDCX, vcpu->kvm)) { /* * Pages already added are reclaimed by the vcpu_free * method, but the rest are freed here. @@ -2915,10 +2899,8 @@ static int tdx_td_vcpu_init(struct kvm_vcpu *vcpu, u64 vcpu_rcx) } err = tdh_vp_init(&tdx->vp, vcpu_rcx, vcpu->vcpu_id); - if (KVM_BUG_ON(err, vcpu->kvm)) { - pr_tdx_error(TDH_VP_INIT, err); + if (TDX_BUG_ON(err, TDH_VP_INIT, vcpu->kvm)) return -EIO; - } vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE; From 55560b6be5bc39384917ff456d1c9ba0a3790277 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:42 -0700 Subject: [PATCH 19/33] KVM: TDX: Derive error argument names from the local variable names When printing SEAMCALL errors, use the name of the variable holding an error parameter instead of the register from whence it came, so that flows which use descriptive variable names will similarly print descriptive error messages. Suggested-by: Rick Edgecombe Reviewed-by: Binbin Wu Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-20-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 5a30d77375cc..a9d1aabbefbf 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -41,14 +41,15 @@ #define TDX_BUG_ON(__err, __fn, __kvm) \ __TDX_BUG_ON(__err, #__fn, __kvm, "%s", "") -#define TDX_BUG_ON_1(__err, __fn, __rcx, __kvm) \ - __TDX_BUG_ON(__err, #__fn, __kvm, ", rcx 0x%llx", __rcx) +#define TDX_BUG_ON_1(__err, __fn, a1, __kvm) \ + __TDX_BUG_ON(__err, #__fn, __kvm, ", " #a1 " 0x%llx", a1) -#define TDX_BUG_ON_2(__err, __fn, __rcx, __rdx, __kvm) \ - __TDX_BUG_ON(__err, #__fn, __kvm, ", rcx 0x%llx, rdx 0x%llx", __rcx, __rdx) +#define TDX_BUG_ON_2(__err, __fn, a1, a2, __kvm) \ + __TDX_BUG_ON(__err, #__fn, __kvm, ", " #a1 " 0x%llx, " #a2 " 0x%llx", a1, a2) -#define TDX_BUG_ON_3(__err, __fn, __rcx, __rdx, __r8, __kvm) \ - __TDX_BUG_ON(__err, #__fn, __kvm, ", rcx 0x%llx, rdx 0x%llx, r8 0x%llx", __rcx, __rdx, __r8) +#define TDX_BUG_ON_3(__err, __fn, a1, a2, a3, __kvm) \ + __TDX_BUG_ON(__err, #__fn, __kvm, ", " #a1 " 0x%llx, " #a2 ", 0x%llx, " #a3 " 0x%llx", \ + a1, a2, a3) bool enable_tdx __ro_after_init; From 2ff14116982c663066f3cdb4e2af5dfa7a812caa Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:43 -0700 Subject: [PATCH 20/33] KVM: TDX: Assert that mmu_lock is held for write when removing S-EPT entries Unconditionally assert that mmu_lock is held for write when removing S-EPT entries, not just when removing S-EPT entries triggers certain conditions, e.g. needs to do TDH_MEM_TRACK or kick vCPUs out of the guest. Conditionally asserting implies that it's safe to hold mmu_lock for read when those paths aren't hit, which is simply not true, as KVM doesn't support removing S-EPT entries under read-lock. Only two paths lead to remove_external_spte(), and both paths asserts that mmu_lock is held for write (tdp_mmu_set_spte() via lockdep, and handle_removed_pt() via KVM_BUG_ON()). Deliberately leave lockdep assertions in the "no vCPUs" helpers to document that wait_for_sept_zap is guarded by holding mmu_lock for write, and keep the conditional assert in tdx_track() as well, but with a comment to help explain why holding mmu_lock for write matters (above and beyond why tdx_sept_remove_private_spte()'s requirements). Reviewed-by: Binbin Wu Reviewed-by: Kai Huang Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-21-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index a9d1aabbefbf..ee17c8aacfa4 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -1715,6 +1715,11 @@ static void tdx_track(struct kvm *kvm) if (unlikely(kvm_tdx->state != TD_STATE_RUNNABLE)) return; + /* + * The full sequence of TDH.MEM.TRACK and forcing vCPUs out of guest + * mode must be serialized, as TDH.MEM.TRACK will fail if the previous + * tracking epoch hasn't completed. + */ lockdep_assert_held_write(&kvm->mmu_lock); err = tdh_mem_track(&kvm_tdx->td); @@ -1762,6 +1767,8 @@ static void tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn, gpa_t gpa = gfn_to_gpa(gfn); u64 err, entry, level_state; + lockdep_assert_held_write(&kvm->mmu_lock); + /* * HKID is released after all private pages have been removed, and set * before any might be populated. Warn if zapping is attempted when From 3d626ce5a8cca64eb6d317eef4b24b70a0e5b27b Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:44 -0700 Subject: [PATCH 21/33] KVM: TDX: Add macro to retry SEAMCALLs when forcing vCPUs out of guest Add a macro to handle kicking vCPUs out of the guest and retrying SEAMCALLs on TDX_OPERAND_BUSY instead of providing small helpers to be used by each SEAMCALL. Wrapping the SEAMCALLs in a macro makes it a little harder to tease out which SEAMCALL is being made, but significantly reduces the amount of copy+paste code, and makes it all but impossible to leave an elevated wait_for_sept_zap. Reviewed-by: Binbin Wu Reviewed-by: Kai Huang Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-22-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 82 +++++++++++++++++------------------------- 1 file changed, 33 insertions(+), 49 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index ee17c8aacfa4..88c85fd82a0e 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -294,25 +294,34 @@ static inline void tdx_disassociate_vp(struct kvm_vcpu *vcpu) vcpu->cpu = -1; } -static void tdx_no_vcpus_enter_start(struct kvm *kvm) -{ - struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm); - - lockdep_assert_held_write(&kvm->mmu_lock); - - WRITE_ONCE(kvm_tdx->wait_for_sept_zap, true); - - kvm_make_all_cpus_request(kvm, KVM_REQ_OUTSIDE_GUEST_MODE); -} - -static void tdx_no_vcpus_enter_stop(struct kvm *kvm) -{ - struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm); - - lockdep_assert_held_write(&kvm->mmu_lock); - - WRITE_ONCE(kvm_tdx->wait_for_sept_zap, false); -} +/* + * Execute a SEAMCALL related to removing/blocking S-EPT entries, with a single + * retry (if necessary) after forcing vCPUs to exit and wait for the operation + * to complete. All flows that remove/block S-EPT entries run with mmu_lock + * held for write, i.e. are mutually exclusive with each other, but they aren't + * mutually exclusive with running vCPUs, and so can fail with "operand busy" + * if a vCPU acquires a relevant lock in the TDX-Module, e.g. when doing TDCALL. + * + * Note, the retry is guaranteed to succeed, absent KVM and/or TDX-Module bugs. + */ +#define tdh_do_no_vcpus(tdh_func, kvm, args...) \ +({ \ + struct kvm_tdx *__kvm_tdx = to_kvm_tdx(kvm); \ + u64 __err; \ + \ + lockdep_assert_held_write(&kvm->mmu_lock); \ + \ + __err = tdh_func(args); \ + if (unlikely(tdx_operand_busy(__err))) { \ + WRITE_ONCE(__kvm_tdx->wait_for_sept_zap, true); \ + kvm_make_all_cpus_request(kvm, KVM_REQ_OUTSIDE_GUEST_MODE); \ + \ + __err = tdh_func(args); \ + \ + WRITE_ONCE(__kvm_tdx->wait_for_sept_zap, false); \ + } \ + __err; \ +}) /* TDH.PHYMEM.PAGE.RECLAIM is allowed only when destroying the TD. */ static int __tdx_reclaim_page(struct page *page) @@ -1722,14 +1731,7 @@ static void tdx_track(struct kvm *kvm) */ lockdep_assert_held_write(&kvm->mmu_lock); - err = tdh_mem_track(&kvm_tdx->td); - if (unlikely(tdx_operand_busy(err))) { - /* After no vCPUs enter, the second retry is expected to succeed */ - tdx_no_vcpus_enter_start(kvm); - err = tdh_mem_track(&kvm_tdx->td); - tdx_no_vcpus_enter_stop(kvm); - } - + err = tdh_do_no_vcpus(tdh_mem_track, kvm, &kvm_tdx->td); TDX_BUG_ON(err, TDH_MEM_TRACK, kvm); kvm_make_all_cpus_request(kvm, KVM_REQ_OUTSIDE_GUEST_MODE); @@ -1781,14 +1783,8 @@ static void tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn, if (KVM_BUG_ON(level != PG_LEVEL_4K, kvm)) return; - err = tdh_mem_range_block(&kvm_tdx->td, gpa, tdx_level, &entry, &level_state); - if (unlikely(tdx_operand_busy(err))) { - /* After no vCPUs enter, the second retry is expected to succeed */ - tdx_no_vcpus_enter_start(kvm); - err = tdh_mem_range_block(&kvm_tdx->td, gpa, tdx_level, &entry, &level_state); - tdx_no_vcpus_enter_stop(kvm); - } - + err = tdh_do_no_vcpus(tdh_mem_range_block, kvm, &kvm_tdx->td, gpa, + tdx_level, &entry, &level_state); if (TDX_BUG_ON_2(err, TDH_MEM_RANGE_BLOCK, entry, level_state, kvm)) return; @@ -1803,20 +1799,8 @@ static void tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn, * with other vcpu sept operation. * Race with TDH.VP.ENTER due to (0-step mitigation) and Guest TDCALLs. */ - err = tdh_mem_page_remove(&kvm_tdx->td, gpa, tdx_level, &entry, - &level_state); - - if (unlikely(tdx_operand_busy(err))) { - /* - * The second retry is expected to succeed after kicking off all - * other vCPUs and prevent them from invoking TDH.VP.ENTER. - */ - tdx_no_vcpus_enter_start(kvm); - err = tdh_mem_page_remove(&kvm_tdx->td, gpa, tdx_level, &entry, - &level_state); - tdx_no_vcpus_enter_stop(kvm); - } - + err = tdh_do_no_vcpus(tdh_mem_page_remove, kvm, &kvm_tdx->td, gpa, + tdx_level, &entry, &level_state); if (TDX_BUG_ON_2(err, TDH_MEM_PAGE_REMOVE, entry, level_state, kvm)) return; From 59d5c1ed6df222791ab7263e5a0c95eea9d83363 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:45 -0700 Subject: [PATCH 22/33] KVM: TDX: Add tdx_get_cmd() helper to get and validate sub-ioctl command Add a helper to copy a kvm_tdx_cmd structure from userspace and verify that must-be-zero fields are indeed zero. No functional change intended. Reviewed-by: Rick Edgecombe Reviewed-by: Kai Huang Reviewed-by: Binbin Wu Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-23-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 35 +++++++++++++++++++++-------------- 1 file changed, 21 insertions(+), 14 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 88c85fd82a0e..f42cc955d49c 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -2792,20 +2792,29 @@ static int tdx_td_finalize(struct kvm *kvm, struct kvm_tdx_cmd *cmd) return 0; } +static int tdx_get_cmd(void __user *argp, struct kvm_tdx_cmd *cmd) +{ + if (copy_from_user(cmd, argp, sizeof(*cmd))) + return -EFAULT; + + /* + * Userspace should never set hw_error. KVM writes hw_error to report + * hardware-defined error back to userspace. + */ + if (cmd->hw_error) + return -EINVAL; + + return 0; +} + int tdx_vm_ioctl(struct kvm *kvm, void __user *argp) { struct kvm_tdx_cmd tdx_cmd; int r; - if (copy_from_user(&tdx_cmd, argp, sizeof(struct kvm_tdx_cmd))) - return -EFAULT; - - /* - * Userspace should never set hw_error. It is used to fill - * hardware-defined error by the kernel. - */ - if (tdx_cmd.hw_error) - return -EINVAL; + r = tdx_get_cmd(argp, &tdx_cmd); + if (r) + return r; mutex_lock(&kvm->lock); @@ -3181,11 +3190,9 @@ int tdx_vcpu_ioctl(struct kvm_vcpu *vcpu, void __user *argp) if (!is_hkid_assigned(kvm_tdx) || kvm_tdx->state == TD_STATE_RUNNABLE) return -EINVAL; - if (copy_from_user(&cmd, argp, sizeof(cmd))) - return -EFAULT; - - if (cmd.hw_error) - return -EINVAL; + ret = tdx_get_cmd(argp, &cmd); + if (ret) + return ret; switch (cmd.id) { case KVM_TDX_INIT_VCPU: From 94428e3ba3258fc2862db3f9999e548d5a2d2a2a Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:46 -0700 Subject: [PATCH 23/33] KVM: TDX: Convert INIT_MEM_REGION and INIT_VCPU to "unlocked" vCPU ioctl Handle the KVM_TDX_INIT_MEM_REGION and KVM_TDX_INIT_VCPU vCPU sub-ioctls in the unlocked variant, i.e. outside of vcpu->mutex, in anticipation of taking kvm->lock along with all other vCPU mutexes, at which point the sub-ioctls _must_ start without vcpu->mutex held. No functional change intended. Reviewed-by: Kai Huang Co-developed-by: Yan Zhao Signed-off-by: Yan Zhao Reviewed-by: Binbin Wu Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-24-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/include/asm/kvm-x86-ops.h | 1 + arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/vmx/main.c | 9 +++++++ arch/x86/kvm/vmx/tdx.c | 42 +++++++++++++++++++++++++----- arch/x86/kvm/vmx/x86_ops.h | 1 + arch/x86/kvm/x86.c | 7 +++++ 6 files changed, 55 insertions(+), 6 deletions(-) diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h index fdf178443f85..de709fb5bd76 100644 --- a/arch/x86/include/asm/kvm-x86-ops.h +++ b/arch/x86/include/asm/kvm-x86-ops.h @@ -128,6 +128,7 @@ KVM_X86_OP(enable_smi_window) KVM_X86_OP_OPTIONAL(dev_get_attr) KVM_X86_OP_OPTIONAL(mem_enc_ioctl) KVM_X86_OP_OPTIONAL(vcpu_mem_enc_ioctl) +KVM_X86_OP_OPTIONAL(vcpu_mem_enc_unlocked_ioctl) KVM_X86_OP_OPTIONAL(mem_enc_register_region) KVM_X86_OP_OPTIONAL(mem_enc_unregister_region) KVM_X86_OP_OPTIONAL(vm_copy_enc_context_from) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 87a5f5100b1d..2bfae1cfa514 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1914,6 +1914,7 @@ struct kvm_x86_ops { int (*dev_get_attr)(u32 group, u64 attr, u64 *val); int (*mem_enc_ioctl)(struct kvm *kvm, void __user *argp); int (*vcpu_mem_enc_ioctl)(struct kvm_vcpu *vcpu, void __user *argp); + int (*vcpu_mem_enc_unlocked_ioctl)(struct kvm_vcpu *vcpu, void __user *argp); int (*mem_enc_register_region)(struct kvm *kvm, struct kvm_enc_region *argp); int (*mem_enc_unregister_region)(struct kvm *kvm, struct kvm_enc_region *argp); int (*vm_copy_enc_context_from)(struct kvm *kvm, unsigned int source_fd); diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c index 0eb2773b2ae2..a46ccd670785 100644 --- a/arch/x86/kvm/vmx/main.c +++ b/arch/x86/kvm/vmx/main.c @@ -831,6 +831,14 @@ static int vt_vcpu_mem_enc_ioctl(struct kvm_vcpu *vcpu, void __user *argp) return tdx_vcpu_ioctl(vcpu, argp); } +static int vt_vcpu_mem_enc_unlocked_ioctl(struct kvm_vcpu *vcpu, void __user *argp) +{ + if (!is_td_vcpu(vcpu)) + return -EINVAL; + + return tdx_vcpu_unlocked_ioctl(vcpu, argp); +} + static int vt_gmem_max_mapping_level(struct kvm *kvm, kvm_pfn_t pfn, bool is_private) { @@ -1005,6 +1013,7 @@ struct kvm_x86_ops vt_x86_ops __initdata = { .mem_enc_ioctl = vt_op_tdx_only(mem_enc_ioctl), .vcpu_mem_enc_ioctl = vt_op_tdx_only(vcpu_mem_enc_ioctl), + .vcpu_mem_enc_unlocked_ioctl = vt_op_tdx_only(vcpu_mem_enc_unlocked_ioctl), .gmem_max_mapping_level = vt_op_tdx_only(gmem_max_mapping_level) }; diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index f42cc955d49c..3b4d62a3bf31 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -3181,6 +3181,42 @@ static int tdx_vcpu_init_mem_region(struct kvm_vcpu *vcpu, struct kvm_tdx_cmd *c return ret; } +int tdx_vcpu_unlocked_ioctl(struct kvm_vcpu *vcpu, void __user *argp) +{ + struct kvm_tdx *kvm_tdx = to_kvm_tdx(vcpu->kvm); + struct kvm_tdx_cmd cmd; + int r; + + r = tdx_get_cmd(argp, &cmd); + if (r) + return r; + + if (!is_hkid_assigned(kvm_tdx) || kvm_tdx->state == TD_STATE_RUNNABLE) + return -EINVAL; + + if (mutex_lock_killable(&vcpu->mutex)) + return -EINTR; + + vcpu_load(vcpu); + + switch (cmd.id) { + case KVM_TDX_INIT_MEM_REGION: + r = tdx_vcpu_init_mem_region(vcpu, &cmd); + break; + case KVM_TDX_INIT_VCPU: + r = tdx_vcpu_init(vcpu, &cmd); + break; + default: + r = -ENOIOCTLCMD; + break; + } + + vcpu_put(vcpu); + + mutex_unlock(&vcpu->mutex); + return r; +} + int tdx_vcpu_ioctl(struct kvm_vcpu *vcpu, void __user *argp) { struct kvm_tdx *kvm_tdx = to_kvm_tdx(vcpu->kvm); @@ -3195,12 +3231,6 @@ int tdx_vcpu_ioctl(struct kvm_vcpu *vcpu, void __user *argp) return ret; switch (cmd.id) { - case KVM_TDX_INIT_VCPU: - ret = tdx_vcpu_init(vcpu, &cmd); - break; - case KVM_TDX_INIT_MEM_REGION: - ret = tdx_vcpu_init_mem_region(vcpu, &cmd); - break; case KVM_TDX_GET_CPUID: ret = tdx_vcpu_get_cpuid(vcpu, &cmd); break; diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h index 9697368d65b3..a7a870919580 100644 --- a/arch/x86/kvm/vmx/x86_ops.h +++ b/arch/x86/kvm/vmx/x86_ops.h @@ -149,6 +149,7 @@ int tdx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr); int tdx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr); int tdx_vcpu_ioctl(struct kvm_vcpu *vcpu, void __user *argp); +int tdx_vcpu_unlocked_ioctl(struct kvm_vcpu *vcpu, void __user *argp); void tdx_flush_tlb_current(struct kvm_vcpu *vcpu); void tdx_flush_tlb_all(struct kvm_vcpu *vcpu); diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index b85cb213a336..593fccc9cf1c 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -7243,6 +7243,13 @@ static int kvm_vm_ioctl_set_clock(struct kvm *kvm, void __user *argp) long kvm_arch_vcpu_unlocked_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg) { + struct kvm_vcpu *vcpu = filp->private_data; + void __user *argp = (void __user *)arg; + + if (ioctl == KVM_MEMORY_ENCRYPT_OP && + kvm_x86_ops.vcpu_mem_enc_unlocked_ioctl) + return kvm_x86_call(vcpu_mem_enc_unlocked_ioctl)(vcpu, argp); + return -ENOIOCTLCMD; } From 0b76e827b29db17a37870a71814e347970394c78 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:47 -0700 Subject: [PATCH 24/33] KVM: TDX: Use guard() to acquire kvm->lock in tdx_vm_ioctl() Use guard() in tdx_vm_ioctl() to tidy up the code a small amount, but more importantly to minimize the diff of a future change, which will use guard-like semantics to acquire and release multiple locks. No functional change intended. Reviewed-by: Rick Edgecombe Reviewed-by: Kai Huang Reviewed-by: Binbin Wu Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-25-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 3b4d62a3bf31..a4818d9acbd5 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -2816,7 +2816,7 @@ int tdx_vm_ioctl(struct kvm *kvm, void __user *argp) if (r) return r; - mutex_lock(&kvm->lock); + guard(mutex)(&kvm->lock); switch (tdx_cmd.id) { case KVM_TDX_CAPABILITIES: @@ -2829,15 +2829,12 @@ int tdx_vm_ioctl(struct kvm *kvm, void __user *argp) r = tdx_td_finalize(kvm, &tdx_cmd); break; default: - r = -EINVAL; - goto out; + return -EINVAL; } if (copy_to_user(argp, &tdx_cmd, sizeof(struct kvm_tdx_cmd))) - r = -EFAULT; + return -EFAULT; -out: - mutex_unlock(&kvm->lock); return r; } From f26061fe2c259d6f07f641fc8fe677637e06421b Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:48 -0700 Subject: [PATCH 25/33] KVM: TDX: Don't copy "cmd" back to userspace for KVM_TDX_CAPABILITIES Don't copy the kvm_tdx_cmd structure back to userspace when handling KVM_TDX_CAPABILITIES, as tdx_get_capabilities() doesn't modify hw_error or any other fields. Opportunistically hoist the call to tdx_get_capabilities() outside of the kvm->lock critical section, as getting the capabilities doesn't touch the VM in any way, e.g. doesn't even take @kvm. Suggested-by: Kai Huang Reviewed-by: Kai Huang Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-26-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index a4818d9acbd5..73842b762e5f 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -2816,12 +2816,12 @@ int tdx_vm_ioctl(struct kvm *kvm, void __user *argp) if (r) return r; + if (tdx_cmd.id == KVM_TDX_CAPABILITIES) + return tdx_get_capabilities(&tdx_cmd); + guard(mutex)(&kvm->lock); switch (tdx_cmd.id) { - case KVM_TDX_CAPABILITIES: - r = tdx_get_capabilities(&tdx_cmd); - break; case KVM_TDX_INIT_VM: r = tdx_td_init(kvm, &tdx_cmd); break; From 15945e9ec1951d8cf7c1a7ec8c441017969d5aa1 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:49 -0700 Subject: [PATCH 26/33] KVM: TDX: Guard VM state transitions with "all" the locks Acquire kvm->lock, kvm->slots_lock, and all vcpu->mutex locks when servicing ioctls that (a) transition the TD to a new state, i.e. when doing INIT or FINALIZE or (b) are only valid if the TD is in a specific state, i.e. when initializing a vCPU or memory region. Acquiring "all" the locks fixes several KVM_BUG_ON() situations where a SEAMCALL can fail due to racing actions, e.g. if tdh_vp_create() contends with either tdh_mr_extend() or tdh_mr_finalize(). For all intents and purposes, the paths in question are fully serialized, i.e. there's no reason to try and allow anything remotely interesting to happen. Smack 'em with a big hammer instead of trying to be "nice". Acquire kvm->lock to prevent VM-wide things from happening, slots_lock to prevent kvm_mmu_zap_all_fast(), and _all_ vCPU mutexes to prevent vCPUs from interefering. Use the recently-renamed kvm_arch_vcpu_unlocked_ioctl() to service the vCPU-scoped ioctls to avoid a lock inversion problem, e.g. due to taking vcpu->mutex outside kvm->lock. See also commit ecf371f8b02d ("KVM: SVM: Reject SEV{-ES} intra host migration if vCPU creation is in-flight"), which fixed a similar bug with SEV intra-host migration where an in-flight vCPU creation could race with a VM-wide state transition. Define a fancy new CLASS to handle the lock+check => unlock logic with guard()-like syntax: CLASS(tdx_vm_state_guard, guard)(kvm); if (IS_ERR(guard)) return PTR_ERR(guard); to simplify juggling the many locks. Note! Take kvm->slots_lock *after* all vcpu->mutex locks, as per KVM's soon-to-be-documented lock ordering rules[1]. Link: https://lore.kernel.org/all/20251016235538.171962-1-seanjc@google.com [1] Reported-by: Yan Zhao Closes: https://lore.kernel.org/all/aLFiPq1smdzN3Ary@yzhao56-desk.sh.intel.com Reviewed-by: Kai Huang Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-27-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 59 +++++++++++++++++++++++++++++++++++------- 1 file changed, 49 insertions(+), 10 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 73842b762e5f..ab62aee2aaa4 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -2653,6 +2653,46 @@ err_out: return -EIO; } +typedef void *tdx_vm_state_guard_t; + +static tdx_vm_state_guard_t tdx_acquire_vm_state_locks(struct kvm *kvm) +{ + int r; + + mutex_lock(&kvm->lock); + + if (kvm->created_vcpus != atomic_read(&kvm->online_vcpus)) { + r = -EBUSY; + goto out_err; + } + + r = kvm_lock_all_vcpus(kvm); + if (r) + goto out_err; + + /* + * Note the unintuitive ordering! vcpu->mutex must be taken outside + * kvm->slots_lock! + */ + mutex_lock(&kvm->slots_lock); + return kvm; + +out_err: + mutex_unlock(&kvm->lock); + return ERR_PTR(r); +} + +static void tdx_release_vm_state_locks(struct kvm *kvm) +{ + mutex_unlock(&kvm->slots_lock); + kvm_unlock_all_vcpus(kvm); + mutex_unlock(&kvm->lock); +} + +DEFINE_CLASS(tdx_vm_state_guard, tdx_vm_state_guard_t, + if (!IS_ERR(_T)) tdx_release_vm_state_locks(_T), + tdx_acquire_vm_state_locks(kvm), struct kvm *kvm); + static int tdx_td_init(struct kvm *kvm, struct kvm_tdx_cmd *cmd) { struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm); @@ -2774,8 +2814,6 @@ static int tdx_td_finalize(struct kvm *kvm, struct kvm_tdx_cmd *cmd) { struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm); - guard(mutex)(&kvm->slots_lock); - if (!is_hkid_assigned(kvm_tdx) || kvm_tdx->state == TD_STATE_RUNNABLE) return -EINVAL; @@ -2819,7 +2857,9 @@ int tdx_vm_ioctl(struct kvm *kvm, void __user *argp) if (tdx_cmd.id == KVM_TDX_CAPABILITIES) return tdx_get_capabilities(&tdx_cmd); - guard(mutex)(&kvm->lock); + CLASS(tdx_vm_state_guard, guard)(kvm); + if (IS_ERR(guard)) + return PTR_ERR(guard); switch (tdx_cmd.id) { case KVM_TDX_INIT_VM: @@ -3123,8 +3163,6 @@ static int tdx_vcpu_init_mem_region(struct kvm_vcpu *vcpu, struct kvm_tdx_cmd *c if (tdx->state != VCPU_TD_STATE_INITIALIZED) return -EINVAL; - guard(mutex)(&kvm->slots_lock); - /* Once TD is finalized, the initial guest memory is fixed. */ if (kvm_tdx->state == TD_STATE_RUNNABLE) return -EINVAL; @@ -3180,7 +3218,8 @@ static int tdx_vcpu_init_mem_region(struct kvm_vcpu *vcpu, struct kvm_tdx_cmd *c int tdx_vcpu_unlocked_ioctl(struct kvm_vcpu *vcpu, void __user *argp) { - struct kvm_tdx *kvm_tdx = to_kvm_tdx(vcpu->kvm); + struct kvm *kvm = vcpu->kvm; + struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm); struct kvm_tdx_cmd cmd; int r; @@ -3188,12 +3227,13 @@ int tdx_vcpu_unlocked_ioctl(struct kvm_vcpu *vcpu, void __user *argp) if (r) return r; + CLASS(tdx_vm_state_guard, guard)(kvm); + if (IS_ERR(guard)) + return PTR_ERR(guard); + if (!is_hkid_assigned(kvm_tdx) || kvm_tdx->state == TD_STATE_RUNNABLE) return -EINVAL; - if (mutex_lock_killable(&vcpu->mutex)) - return -EINTR; - vcpu_load(vcpu); switch (cmd.id) { @@ -3210,7 +3250,6 @@ int tdx_vcpu_unlocked_ioctl(struct kvm_vcpu *vcpu, void __user *argp) vcpu_put(vcpu); - mutex_unlock(&vcpu->mutex); return r; } From ad44aa4c5d3f40f4254a25a2ebab8cb9be0e37a3 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:50 -0700 Subject: [PATCH 27/33] KVM: TDX: Bug the VM if extending the initial measurement fails WARN and terminate the VM if TDH_MR_EXTEND fails, as extending the measurement should fail if and only if there is a KVM bug, or if the S-EPT mapping is invalid. Now that KVM makes all state transitions mutually exclusive via tdx_vm_state_guard, it should be impossible for S-EPT mappings to be removed between kvm_tdp_mmu_map_private_pfn() and tdh_mr_extend(). Holding slots_lock prevents zaps due to memslot updates, filemap_invalidate_lock() prevents zaps due to guest_memfd PUNCH_HOLE, vcpu->mutex locks prevents updates from other vCPUs, kvm->lock prevents VM-scoped ioctls from creating havoc (e.g. by creating new vCPUs), and all usage of kvm_zap_gfn_range() is mutually exclusive with S-EPT entries that can be used for the initial image. For kvm_zap_gfn_range(), the call from sev.c is obviously mutually exclusive, TDX disallows KVM_X86_QUIRK_IGNORE_GUEST_PAT so the same goes for kvm_noncoherent_dma_assignment_start_or_stop(), and __kvm_set_or_clear_apicv_inhibit() is blocked by virtue of holding all VM and vCPU mutexes (and the APIC page has its own KVM-internal memslot that is never created for TDX VMs, and so can't possibly be used for the initial image, which means that too is mutually exclusive irrespective of locking). Opportunistically return early if the region doesn't need to be measured in order to reduce line lengths and avoid wraps. Similarly, immediately and explicitly return if TDH_MR_EXTEND fails to make it clear that KVM needs to bail entirely if extending the measurement fails. Reviewed-by: Binbin Wu Reviewed-by: Kai Huang Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-28-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 24 +++++++++++++----------- 1 file changed, 13 insertions(+), 11 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index ab62aee2aaa4..977cc41c96b4 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -3133,21 +3133,23 @@ static int tdx_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, put_page(src_page); - if (ret) + if (ret || !(arg->flags & KVM_TDX_MEASURE_MEMORY_REGION)) return ret; - if (arg->flags & KVM_TDX_MEASURE_MEMORY_REGION) { - for (i = 0; i < PAGE_SIZE; i += TDX_EXTENDMR_CHUNKSIZE) { - err = tdh_mr_extend(&kvm_tdx->td, gpa + i, &entry, - &level_state); - if (err) { - ret = -EIO; - break; - } - } + /* + * Note, MR.EXTEND can fail if the S-EPT mapping is somehow removed + * between mapping the pfn and now, but slots_lock prevents memslot + * updates, filemap_invalidate_lock() prevents guest_memfd updates, + * mmu_notifier events can't reach S-EPT entries, and KVM's internal + * zapping flows are mutually exclusive with S-EPT mappings. + */ + for (i = 0; i < PAGE_SIZE; i += TDX_EXTENDMR_CHUNKSIZE) { + err = tdh_mr_extend(&kvm_tdx->td, gpa + i, &entry, &level_state); + if (TDX_BUG_ON_2(err, TDH_MR_EXTEND, entry, level_state, kvm)) + return -EIO; } - return ret; + return 0; } static int tdx_vcpu_init_mem_region(struct kvm_vcpu *vcpu, struct kvm_tdx_cmd *cmd) From 1e3a825c9ec90f91ef61dc9cbda610d9ec887db8 Mon Sep 17 00:00:00 2001 From: Yan Zhao Date: Thu, 30 Oct 2025 13:09:51 -0700 Subject: [PATCH 28/33] KVM: TDX: Fix list_add corruption during vcpu_load() During vCPU creation, a vCPU may be destroyed immediately after kvm_arch_vcpu_create() (e.g., due to vCPU id confiliction). However, the vcpu_load() inside kvm_arch_vcpu_create() may have associate the vCPU to pCPU via "list_add(&tdx->cpu_list, &per_cpu(associated_tdvcpus, cpu))" before invoking tdx_vcpu_free(). Though there's no need to invoke tdh_vp_flush() on the vCPU, failing to dissociate the vCPU from pCPU (i.e., "list_del(&to_tdx(vcpu)->cpu_list)") will cause list corruption of the per-pCPU list associated_tdvcpus. Then, a later list_add() during vcpu_load() would detect list corruption and print calltrace as shown below. Dissociate a vCPU from its associated pCPU in tdx_vcpu_free() for the vCPUs destroyed immediately after creation which must be in VCPU_TD_STATE_UNINITIALIZED state. kernel BUG at lib/list_debug.c:29! Oops: invalid opcode: 0000 [#2] SMP NOPTI RIP: 0010:__list_add_valid_or_report+0x82/0xd0 Call Trace: tdx_vcpu_load+0xa8/0x120 vt_vcpu_load+0x25/0x30 kvm_arch_vcpu_load+0x81/0x300 vcpu_load+0x55/0x90 kvm_arch_vcpu_create+0x24f/0x330 kvm_vm_ioctl_create_vcpu+0x1b1/0x53 kvm_vm_ioctl+0xc2/0xa60 __x64_sys_ioctl+0x9a/0xf0 x64_sys_call+0x10ee/0x20d0 do_syscall_64+0xc3/0x470 entry_SYSCALL_64_after_hwframe+0x77/0x7f Fixes: d789fa6efac9 ("KVM: TDX: Handle vCPU dissociation") Signed-off-by: Yan Zhao Reviewed-by: Kai Huang Reviewed-by: Yan Zhao Tested-by: Yan Zhao Tested-by: Kai Huang Link: https://patch.msgid.link/20251030200951.3402865-29-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 43 +++++++++++++++++++++++++++++++++++++----- 1 file changed, 38 insertions(+), 5 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 977cc41c96b4..865d18b34988 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -843,19 +843,52 @@ void tdx_vcpu_put(struct kvm_vcpu *vcpu) tdx_prepare_switch_to_host(vcpu); } +/* + * Life cycles for a TD and a vCPU: + * 1. KVM_CREATE_VM ioctl. + * TD state is TD_STATE_UNINITIALIZED. + * hkid is not assigned at this stage. + * 2. KVM_TDX_INIT_VM ioctl. + * TD transitions to TD_STATE_INITIALIZED. + * hkid is assigned after this stage. + * 3. KVM_CREATE_VCPU ioctl. (only when TD is TD_STATE_INITIALIZED). + * 3.1 tdx_vcpu_create() transitions vCPU state to VCPU_TD_STATE_UNINITIALIZED. + * 3.2 vcpu_load() and vcpu_put() in kvm_arch_vcpu_create(). + * 3.3 (conditional) if any error encountered after kvm_arch_vcpu_create() + * kvm_arch_vcpu_destroy() --> tdx_vcpu_free(). + * 4. KVM_TDX_INIT_VCPU ioctl. + * tdx_vcpu_init() transitions vCPU state to VCPU_TD_STATE_INITIALIZED. + * vCPU control structures are allocated at this stage. + * 5. kvm_destroy_vm(). + * 5.1 tdx_mmu_release_hkid(): (1) tdh_vp_flush(), disassociates all vCPUs. + * (2) puts hkid to !assigned state. + * 5.2 kvm_destroy_vcpus() --> tdx_vcpu_free(): + * transitions vCPU to VCPU_TD_STATE_UNINITIALIZED state. + * 5.3 tdx_vm_destroy() + * transitions TD to TD_STATE_UNINITIALIZED state. + * + * tdx_vcpu_free() can be invoked only at 3.3 or 5.2. + * - If at 3.3, hkid is still assigned, but the vCPU must be in + * VCPU_TD_STATE_UNINITIALIZED state. + * - if at 5.2, hkid must be !assigned and all vCPUs must be in + * VCPU_TD_STATE_INITIALIZED state and have been dissociated. + */ void tdx_vcpu_free(struct kvm_vcpu *vcpu) { struct kvm_tdx *kvm_tdx = to_kvm_tdx(vcpu->kvm); struct vcpu_tdx *tdx = to_tdx(vcpu); int i; + if (vcpu->cpu != -1) { + KVM_BUG_ON(tdx->state == VCPU_TD_STATE_INITIALIZED, vcpu->kvm); + tdx_flush_vp_on_cpu(vcpu); + return; + } + /* * It is not possible to reclaim pages while hkid is assigned. It might - * be assigned if: - * 1. the TD VM is being destroyed but freeing hkid failed, in which - * case the pages are leaked - * 2. TD VCPU creation failed and this on the error path, in which case - * there is nothing to do anyway + * be assigned if the TD VM is being destroyed but freeing hkid failed, + * in which case the pages are leaked. */ if (is_hkid_assigned(kvm_tdx)) return; From 9a89894f30d5795c5ac46a9ee9c009d610306025 Mon Sep 17 00:00:00 2001 From: Rick Edgecombe Date: Mon, 27 Oct 2025 17:28:24 -0700 Subject: [PATCH 29/33] KVM: TDX: Take MMU lock around tdh_vp_init() Take MMU lock around tdh_vp_init() in KVM_TDX_INIT_VCPU to prevent meeting contention during retries in some no-fail MMU paths. The TDX module takes various try-locks internally, which can cause SEAMCALLs to return an error code when contention is met. Dealing with an error in some of the MMU paths that make SEAMCALLs is not straight forward, so KVM takes steps to ensure that these will meet no contention during a single BUSY error retry. The whole scheme relies on KVM to take appropriate steps to avoid making any SEAMCALLs that could contend while the retry is happening. Unfortunately, there is a case where contention could be met if userspace does something unusual. Specifically, hole punching a gmem fd while initializing the TD vCPU. The impact would be triggering a KVM_BUG_ON(). The resource being contended is called the "TDR resource" in TDX docs parlance. The tdh_vp_init() can take this resource as exclusive if the 'version' passed is 1, which happens to be version the kernel passes. The various MMU operations (tdh_mem_range_block(), tdh_mem_track() and tdh_mem_page_remove()) take it as shared. There isn't a KVM lock that maps conceptually and in a lock order friendly way to the TDR lock. So to minimize infrastructure, just take MMU lock around tdh_vp_init(). This makes the operations we care about mutually exclusive. Since the other operations are under a write mmu_lock, the code could just take the lock for read, however this is weirdly inverted from the actual underlying resource being contended. Since this is covering an edge case that shouldn't be hit in normal usage, be a little less weird and take the mmu_lock for write around the call. Fixes: 02ab57707bdb ("KVM: TDX: Implement hooks to propagate changes of TDP MMU mirror page table") Reported-by: Yan Zhao Suggested-by: Yan Zhao Link: https://patch.msgid.link/20251028002824.1470939-1-rick.p.edgecombe@intel.com Signed-off-by: Rick Edgecombe [sean: tweak comment and capture PUNCH_HOLE interaction] Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 865d18b34988..b5087d40f50b 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -2969,9 +2969,20 @@ static int tdx_td_vcpu_init(struct kvm_vcpu *vcpu, u64 vcpu_rcx) } } - err = tdh_vp_init(&tdx->vp, vcpu_rcx, vcpu->vcpu_id); - if (TDX_BUG_ON(err, TDH_VP_INIT, vcpu->kvm)) - return -EIO; + /* + * tdh_vp_init() can take an exclusive lock of the TDR resource inside + * the TDX-Module. The TDR resource is also taken as shared in several + * no-fail MMU paths, which could return TDX_OPERAND_BUSY on contention + * (TDX-Module locks are try-lock implementations with no slow path). + * Take mmu_lock for write to reflect the nature of the lock taken by + * the TDX-Module, and to ensure the no-fail MMU paths succeed, e.g. if + * a concurrent PUNCH_HOLE on guest_memfd triggers removal of SPTEs. + */ + scoped_guard(write_lock, &vcpu->kvm->mmu_lock) { + err = tdh_vp_init(&tdx->vp, vcpu_rcx, vcpu->vcpu_id); + if (TDX_BUG_ON(err, TDH_VP_INIT, vcpu->kvm)) + return -EIO; + } vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE; From 228add34dc2f197539c497bf5573d75cd58f5c61 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Mon, 3 Nov 2025 15:44:37 -0800 Subject: [PATCH 30/33] KVM: TDX: Remove __user annotation from kernel pointer Separate __user pointer variable declaration from kernel one. There are two 'kvm_cpuid2' pointers involved here. There's an "input" side: 'td_cpuid' which is a normal kernel pointer and an 'output' side. The output here is userspace and there is an attempt at properly annotating the variable with __user: struct kvm_cpuid2 __user *output, *td_cpuid; But, alas, this is wrong. The __user in the definition applies to both 'output' and 'td_cpuid'. Sparse notices the address space mismatch and will complain about it. Fix it up by completely separating the two definitions so that it is obviously correct without even having to know what the C syntax rules even are. Signed-off-by: Dave Hansen Fixes: 488808e682e7 ("KVM: x86: Introduce KVM_TDX_GET_CPUID") Reviewed-by: Rick Edgecombe Cc: Xiaoyao Li Cc: Sean Christopherson Cc: Paolo Bonzini Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: x86@kernel.org Cc: "H. Peter Anvin" Cc: "Kirill A. Shutemov" Cc: Rick Edgecombe Cc: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org Reviewed-by: Xiaoyao Li Acked-by: Kiryl Shutsemau Link: https://patch.msgid.link/20251103234437.A0532420@davehans-spike.ostc.intel.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index b5087d40f50b..3525e0e9d073 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -3038,7 +3038,8 @@ static int tdx_vcpu_get_cpuid_leaf(struct kvm_vcpu *vcpu, u32 leaf, int *entry_i static int tdx_vcpu_get_cpuid(struct kvm_vcpu *vcpu, struct kvm_tdx_cmd *cmd) { - struct kvm_cpuid2 __user *output, *td_cpuid; + struct kvm_cpuid2 __user *output; + struct kvm_cpuid2 *td_cpuid; int r = 0, i = 0, leaf; u32 level; From 27376465e945c11ad13c1e1d877ed318be010062 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Mon, 3 Nov 2025 15:44:39 -0800 Subject: [PATCH 31/33] KVM: TDX: Fix sparse warnings from using 0 for NULL Stop using 0 for NULL. sparse moans: ... arch/x86/kvm/vmx/tdx.c:859:38: warning: Using plain integer as NULL pointer for several TDX pointer initializations. While I love a good ptr=0 now and then, it's good to have quiet sparse builds. Signed-off-by: Dave Hansen Fixes: a50f673f25e0 ("KVM: TDX: Do TDX specific vcpu initialization") Fixes: 8d032b683c29 ("KVM: TDX: create/destroy VM structure") Reviewed-by: Rick Edgecombe Cc: Xiaoyao Li Cc: Sean Christopherson Cc: Paolo Bonzini Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: x86@kernel.org Cc: "H. Peter Anvin" Cc: "Kirill A. Shutemov" Cc: Rick Edgecombe Cc: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org Reviewed-by: Xiaoyao Li Acked-by: Kiryl Shutsemau Link: https://patch.msgid.link/20251103234439.DC8227E4@davehans-spike.ostc.intel.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 3525e0e9d073..0ffca14c1071 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -903,7 +903,7 @@ void tdx_vcpu_free(struct kvm_vcpu *vcpu) } if (tdx->vp.tdvpr_page) { tdx_reclaim_control_page(tdx->vp.tdvpr_page); - tdx->vp.tdvpr_page = 0; + tdx->vp.tdvpr_page = NULL; tdx->vp.tdvpr_pa = 0; } @@ -2581,7 +2581,7 @@ free_tdcs: free_tdr: if (tdr_page) __free_page(tdr_page); - kvm_tdx->td.tdr_page = 0; + kvm_tdx->td.tdr_page = NULL; free_hkid: tdx_hkid_free(kvm_tdx); @@ -3000,7 +3000,7 @@ free_tdcx: free_tdvpr: if (tdx->vp.tdvpr_page) __free_page(tdx->vp.tdvpr_page); - tdx->vp.tdvpr_page = 0; + tdx->vp.tdvpr_page = NULL; tdx->vp.tdvpr_pa = 0; return ret; From 11b79f8318aefc7ddfd12668fd1d80bde1c9f7bc Mon Sep 17 00:00:00 2001 From: Thorsten Blum Date: Fri, 17 Oct 2025 23:39:14 +0200 Subject: [PATCH 32/33] KVM: TDX: Check size of user's kvm_tdx_capabilities array before allocating When userspace is getting TDX capabilities, retrieve and check the number of user entries before allocating kernel scratch space to avoid having to unwind the allocation if get_user() fails or if 'user_caps' is too small to fit 'caps'. Signed-off-by: Thorsten Blum Tested-by: Rick Edgecombe Link: https://patch.msgid.link/20251017213914.167301-1-thorsten.blum@linux.dev [sean: split to separate patch] Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 18 +++++++----------- 1 file changed, 7 insertions(+), 11 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 0ffca14c1071..cc751c088476 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -2224,23 +2224,19 @@ static int tdx_get_capabilities(struct kvm_tdx_cmd *cmd) if (cmd->flags) return -EINVAL; + user_caps = u64_to_user_ptr(cmd->data); + if (get_user(nr_user_entries, &user_caps->cpuid.nent)) + return -EFAULT; + + if (nr_user_entries < td_conf->num_cpuid_config) + return -E2BIG; + caps = kzalloc(sizeof(*caps) + sizeof(struct kvm_cpuid_entry2) * td_conf->num_cpuid_config, GFP_KERNEL); if (!caps) return -ENOMEM; - user_caps = u64_to_user_ptr(cmd->data); - if (get_user(nr_user_entries, &user_caps->cpuid.nent)) { - ret = -EFAULT; - goto out; - } - - if (nr_user_entries < td_conf->num_cpuid_config) { - ret = -E2BIG; - goto out; - } - ret = init_kvm_tdx_caps(td_conf, caps); if (ret) goto out; From 398180f93cf3c7bb0ee3f512b139ad01843f3ddf Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Mon, 10 Nov 2025 13:24:53 -0800 Subject: [PATCH 33/33] KVM: TDX: Use struct_size to simplify tdx_get_capabilities() Use struct_size() instead of manually calculating the number of bytes to allocate for 'caps', including the nested flexible array, and copy all of 'caps' to user space with a single copy_to_user() call (thanks to the full size being provided by struct_size()). Signed-off-by: Thorsten Blum Tested-by: Rick Edgecombe Link: https://patch.msgid.link/20251017213914.167301-1-thorsten.blum@linux.dev [sean: separate from swap of get_user() vs. kzalloc() ordering] Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 13 ++++--------- 1 file changed, 4 insertions(+), 9 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index cc751c088476..a940a54ca593 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -2231,9 +2231,8 @@ static int tdx_get_capabilities(struct kvm_tdx_cmd *cmd) if (nr_user_entries < td_conf->num_cpuid_config) return -E2BIG; - caps = kzalloc(sizeof(*caps) + - sizeof(struct kvm_cpuid_entry2) * td_conf->num_cpuid_config, - GFP_KERNEL); + caps = kzalloc(struct_size(caps, cpuid.entries, + td_conf->num_cpuid_config), GFP_KERNEL); if (!caps) return -ENOMEM; @@ -2241,16 +2240,12 @@ static int tdx_get_capabilities(struct kvm_tdx_cmd *cmd) if (ret) goto out; - if (copy_to_user(user_caps, caps, sizeof(*caps))) { + if (copy_to_user(user_caps, caps, struct_size(caps, cpuid.entries, + caps->cpuid.nent))) { ret = -EFAULT; goto out; } - if (copy_to_user(user_caps->cpuid.entries, caps->cpuid.entries, - caps->cpuid.nent * - sizeof(caps->cpuid.entries[0]))) - ret = -EFAULT; - out: /* kfree() accepts NULL. */ kfree(caps);