Re: [Patch v6 18/20] perf/x86/intel: Refill LBR stack for LBR counter events in PMI handler

[sashiko-bot@kernel.org]

> When handling an LBR counter event, the raw LBR counters in the reserved
> field of each LBR entry are cleared after the stack is processed and
> reported to userspace. This prevents raw counter data from leaking.
> 
> However, if multiple events overflow in the same PMI, an LBR counter
> event may not be the first one processed. In that case, the raw LBR
> counters may already have been cleared by the previous LBR event, so the
> later LBR counter event cannot read the correct values.
> 
> Refill the LBR stack before processing an LBR counter event when multiple
> events are handled in a single PMI. This restores the correct raw LBR
> counter data for the event in this corner case.
> 
> This situation is rare, the performance impact from extra refill should
> be negligible.
> 
> Reported-by: Sashiko <sashiko-bot@kernel.org>
> Fixes: 33744916196b ("perf/x86/intel: Support branch counters logging")
> Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261106043257.842864-1-dapeng1.mi@linux.intel.com?part=18