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Date: Sat, 21 Nov 2020 02:36:24 +0000 From: Fenghua Yu <fenghua.yu@...el.com> To: "Thomas Gleixner" <tglx@...utronix.de>, "Borislav Petkov" <bp@...en8.de>, "Ingo Molnar" <mingo@...hat.com>, "Peter Zijlstra" <peterz@...radead.org>, "Tony Luck" <tony.luck@...el.com>, "Randy Dunlap" <rdunlap@...radead.org>, "Xiaoyao Li " <xiaoyao.li@...el.com>, "Ravi V Shankar" <ravi.v.shankar@...el.com> Cc: "linux-kernel" <linux-kernel@...r.kernel.org>, "x86" <x86@...nel.org>, Fenghua Yu <fenghua.yu@...el.com> Subject: [PATCH v3 4/4] 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@...el.com> Reviewed-by: Tony Luck <tony.luck@...el.com> --- Change Log: v3: - Enable Bus Lock Detection when fatal to handle bus lock from non-WB (PeterZ). v1: - Fix a few wording issues (Randy). RFC v2: - Simplify the documentation (Randy). .../admin-guide/kernel-parameters.txt | 31 +++++++++++++++---- 1 file changed, 25 insertions(+), 6 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 44fde25bb221..dcdb4fd3597d 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5051,27 +5051,46 @@ 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 #DB 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. If both features are enabled in + hardware, split lock triggers #AC and bus + lock from non-WB triggers #DB. + + 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 + users. + + 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. -- 2.29.2
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