Documentation/admin-guide: Change doc for split_lock_detect parameter

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@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20210322135325.682257-4-fenghua.yu@intel.com

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 0454572..aef927c 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5100,27 +5100,37 @@
        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 a debug exception for
+                       bus lock detection.
 
                        off     - not enabled
 
-                       warn    - the kernel will emit rate limited warnings
+                       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.
+                                 exception or the #DB exception. This mode is
+                                 the default on CPUs that support split lock
+                                 detection or bus lock detection. Default
+                                 behavior is by #AC if both features are
+                                 enabled in hardware.
 
                        fatal   - the kernel will send SIGBUS to applications
-                                 that trigger the #AC exception.
+                                 that trigger the #AC exception or the #DB
+                                 exception. Default behavior is by #AC if
+                                 both features are enabled in hardware.
 
                        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.