From: sashiko-bot@kernel.org
To: "Dapeng Mi" <dapeng1.mi@linux.intel.com>
Cc: linux-perf-users@vger.kernel.org
Subject: Re: [Patch v3 2/4] perf/x86/amd/lbr: Limit branch snapshots to valid entries
Date: Mon, 19 Oct 2026 07:20:49 +0000 [thread overview]
Message-ID: <sashiko-outbox-176741@kernel.org> (raw)
In-Reply-To: <20261019070836.2972403-3-dapeng1.mi@linux.intel.com>
> From: Sandipan Das <sandipan.das@amd.com>
>
> The branch snapshot callback used by bpf_get_branch_snapshot() copies
> up to x86_pmu.lbr_nr entries from cpuc->lbr_entries[], even when the
> last LBR read kept fewer branches. The entries past lbr_stack.nr are
> invalid, but they end up reaching BPF programs.
>
> Limit copying to lbr_stack.nr entries and also reset lbr_stack.nr when
> amd_pmu_lbr_read() skips reading the registers, so that a stale count
> is never reused.
>
> Fixes: a4d18112e531 ("perf/x86/amd: Support capturing LBR from software events")
> Reported-by: Sashiko <sashiko-bot@kernel.org>
> Closes: https://lore.kernel.org/all/sashiko-outbox-163130@kernel.org/
> Signed-off-by: Sandipan Das <sandipan.das@amd.com>
> Reviewed-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
> Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Sashiko has reviewed this patch and found no issues.
--
Sashiko AI review · https://sashiko.dev/#/patchset/20261019070836.2972403-1-dapeng1.mi@linux.intel.com?part=2
next prev parent reply other threads:[~2026-10-19 7:20 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-19 7:08 [Patch v3 0/4] perf/x86: Limit branch snapshots to valid entries Dapeng Mi
2026-10-19 7:08 ` [Patch v3 1/4] perf/x86: Clamp x86_pmu.lbr_nr to MAX_LBR_ENTRIES Dapeng Mi
2026-10-19 7:28 ` sashiko-bot
2026-10-19 8:44 ` Mi, Dapeng
2026-10-19 7:08 ` [Patch v3 2/4] perf/x86/amd/lbr: Limit branch snapshots to valid entries Dapeng Mi
2026-10-19 7:20 ` sashiko-bot [this message]
2026-10-19 7:08 ` [Patch v3 3/4] perf/x86/intel/lbr: Reset the cached LBR stack in intel_pmu_lbr_reset() Dapeng Mi
2026-10-19 7:30 ` sashiko-bot
2026-10-19 8:47 ` Mi, Dapeng
2026-10-19 7:08 ` [Patch v3 4/4] perf/x86/intel/lbr: Limit branch snapshots to valid entries Dapeng Mi
2026-10-19 7:35 ` sashiko-bot
2026-10-19 9:29 ` Mi, Dapeng
2026-10-19 9:31 ` Mi, Dapeng
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