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Subject[tip: x86/splitlock] Documentation/admin-guide: Change doc for split_lock_detect parameter
The following commit has been merged into the x86/splitlock branch of tip:

Commit-ID: ebca17707e38f2050b188d837bd4646b29a1b0c2
Gitweb: https://git.kernel.org/tip/ebca17707e38f2050b188d837bd4646b29a1b0c2
Author: Fenghua Yu <fenghua.yu@intel.com>
AuthorDate: Mon, 22 Mar 2021 13:53:25
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Sun, 28 Mar 2021 22:52:16 +02:00

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

---
Documentation/admin-guide/kernel-parameters.txt | 22 +++++++++++-----
1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 0454572..aef927c 100644
--- 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.
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