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SubjectRe: [PATCH RFC v2 4/4] Documentation: Change doc for split_lock_detect parameter
From
Date
On 10/28/20 1:28 PM, Fenghua Yu wrote:
> 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>
> Reviewed-by: Tony Luck <tony.luck@intel.com>
> ---
> .../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.
> +

Hi,
This appears to have quite a bit of duplicated lines....

> + 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.
>


--
~Randy

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