From: sashiko-bot@kernel.org
To: "Sandipan Das" <sandipan.das@amd.com>
Cc: linux-perf-users@vger.kernel.org, bpf@vger.kernel.org
Subject: Re: [PATCH] perf/x86/amd/lbr: Limit branch snapshots to valid entries
Date: Wed, 07 Oct 2026 18:19:36 +0000 [thread overview]
Message-ID: <sashiko-outbox-163284@kernel.org> (raw)
In-Reply-To: <20261007181002.4005262-1-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>
Sashiko has reviewed this patch and found no issues. It looks great!
--
Sashiko AI review · https://sashiko.dev/#/patchset/20261007181002.4005262-1-sandipan.das@amd.com?part=1
next prev parent reply other threads:[~2026-10-07 18:19 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-07 18:10 [PATCH] perf/x86/amd/lbr: Limit branch snapshots to valid entries Sandipan Das
2026-10-07 18:19 ` sashiko-bot [this message]
2026-10-12 15:30 ` Peter Zijlstra
2026-10-13 6:44 ` Sandipan Das
2026-10-13 7:46 ` Peter Zijlstra
2026-10-13 12:53 ` Mi, Dapeng
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