docs: kernel-parameters: add kfence parameters

Add a brief summary for KFENCE's kernel command-line parameters in
admin-guide/kernel-parameters.

Link: https://lkml.kernel.org/r/20251222150018.1349672-1-elver@google.com
Signed-off-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Documentation/admin-guide/kernel-parameters.txt

@@ -2917,6 +2917,41 @@ Kernel parameters
 			for Movable pages.  "nn[KMGTPE]", "nn%", and "mirror"
 			are exclusive, so you cannot specify multiple forms.
 
+	kfence.burst=	[MM,KFENCE] The number of additional successive
+			allocations to be attempted through KFENCE for each
+			sample interval.
+			Format: <unsigned integer>
+			Default: 0
+
+	kfence.check_on_panic=
+			[MM,KFENCE] Whether to check all KFENCE-managed objects'
+			canaries on panic.
+			Format: <bool>
+			Default: false
+
+	kfence.deferrable=
+			[MM,KFENCE] Whether to use a deferrable timer to trigger
+			allocations. This avoids forcing CPU wake-ups if the
+			system is idle, at the risk of a less predictable
+			sample interval.
+			Format: <bool>
+			Default: CONFIG_KFENCE_DEFERRABLE
+
+	kfence.sample_interval=
+			[MM,KFENCE] KFENCE's sample interval in milliseconds.
+			Format: <unsigned integer>
+			 0 - Disable KFENCE.
+			>0 - Enabled KFENCE with given sample interval.
+			Default: CONFIG_KFENCE_SAMPLE_INTERVAL
+
+	kfence.skip_covered_thresh=
+			[MM,KFENCE] If pool utilization reaches this threshold
+			(pool usage%), KFENCE limits currently covered
+			allocations of the same source from further filling
+			up the pool.
+			Format: <unsigned integer>
+			Default: 75
+
 	kgdbdbgp=	[KGDB,HW,EARLY] kgdb over EHCI usb debug port.
 			Format: <Controller#>[,poll interval]
 			The controller # is the number of the ehci usb debug