[PATCH RFC v2 4/4] Documentation: Change doc for split_lock_detect parameter

[Fenghua Yu]

Since #DB for bus lock detect changes the split_lock_detect parameter,
update the documentation for the changes.

Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
---
 .../admin-guide/kernel-parameters.txt         | 47 +++++++++++++++----
 1 file changed, 39 insertions(+), 8 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 526d65d8573a..51312484c2b6 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5044,27 +5044,58 @@
 	spia_peddr=
 
 	split_lock_detect=
-			[X86] Enable split lock detection
+			[X86] Enable split lock detection or bus lock detection
 
 			When enabled (and if hardware support is present), atomic
 			instructions that access data across cache line
-			boundaries will result in an alignment check exception.
+			boundaries will result in an alignment check exception
+			for split lock detection or an debug exception for
+			bus lock detection.
 
 			off	- not enabled
 
-			warn	- the kernel will emit rate limited warnings
-				  about applications triggering the #AC
-				  exception. This mode is the default on CPUs
-				  that supports split lock detection.
+			warn	- Default mode.
 
-			fatal	- the kernel will send SIGBUS to applications
-				  that trigger the #AC exception.
+				  If split lock detection is enabled in
+				  hardware, the kernel will emit rate limited
+				  warnings about applications triggering the #AC
+				  exception.
+
+				  If bus lock detection is enabled in hardware,
+				  the kernel will emit rate limited warnings
+				  about applications triggering the #DB
+				  exception.
+
+				  Default behavior is from bus lock detection
+				  if both features are enabled in hardware.
+
+			fatal	- If split lock detection is enabled in
+				  hardware, the kernel will send SIGBUS to
+				  applications that trigger the #AC exception.
+
+				  If bus lock detection is enabled in hardware,
+				  the kernel will send SIGBUS to application
+				  that trigger the #DB exception.
+
+				  Default behavior is from split lock detection
+				  if both are enabled in hardware.
+
+			ratelimit:N
+				  Set rate limit to N bus locks per second
+				  for bus lock detection. 0 < N <= HZ/2 and
+				  N is approximate. Only applied to non root
+				  user.
+
+				  N/A for split lock detection.
 
 			If an #AC exception is hit in the kernel or in
 			firmware (i.e. not while executing in user mode)
 			the kernel will oops in either "warn" or "fatal"
 			mode.
 
+			#DB exception for bus lock is triggered only when
+			CPL > 0.
+
 	srbds=		[X86,INTEL]
 			Control the Special Register Buffer Data Sampling
 			(SRBDS) mitigation.
-- 
2.29.0