From: sashiko-bot@kernel.org
To: "Dapeng Mi" <dapeng1.mi@linux.intel.com>
Cc: linux-perf-users@vger.kernel.org
Subject: Re: [Patch v5 03/18] perf/x86/amd/lbr: Limit branch snapshots to valid entries
Date: Thu, 29 Oct 2026 04:53:44 +0000 [thread overview]
Message-ID: <sashiko-outbox-188714@kernel.org> (raw)
In-Reply-To: <20261029043914.1395147-4-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/20261029043914.1395147-1-dapeng1.mi@linux.intel.com?part=3
next prev parent reply other threads:[~2026-10-29 4:53 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-29 4:38 [Patch v5 00/18] perf/x86: Fix multiple LBR sampling issues Dapeng Mi
2026-10-29 4:38 ` [Patch v5 01/18] perf/x86: Disable LBR if x86_pmu.lbr_nr exceeds MAX_LBR_ENTRIES Dapeng Mi
2026-10-29 5:03 ` sashiko-bot
2026-10-29 9:38 ` Peter Zijlstra
2026-10-29 9:56 ` Mi, Dapeng
2026-10-29 10:19 ` Peter Zijlstra
2026-10-29 4:38 ` [Patch v5 02/18] perf/x86/intel: Validate LBR XSAVE state before updating LBR stack Dapeng Mi
2026-10-29 5:11 ` sashiko-bot
2026-10-29 9:40 ` Peter Zijlstra
2026-10-29 10:09 ` Mi, Dapeng
2026-10-29 4:38 ` [Patch v5 03/18] perf/x86/amd/lbr: Limit branch snapshots to valid entries Dapeng Mi
2026-10-29 4:53 ` sashiko-bot [this message]
2026-10-29 4:39 ` [Patch v5 04/18] perf/x86/intel/lbr: " Dapeng Mi
2026-10-29 4:56 ` sashiko-bot
2026-10-29 4:39 ` [Patch v5 05/18] perf/x86: Add lbr_enabled to track LBR state Dapeng Mi
2026-10-29 5:10 ` sashiko-bot
2026-10-29 4:39 ` [Patch v5 06/18] perf/x86/amd: Avoid re-enabling PMU and LBR for BPF when disabled Dapeng Mi
2026-10-29 5:08 ` sashiko-bot
2026-10-29 4:39 ` [Patch v5 07/18] perf/x86/intel: Add helper to enable PMU without LBR Dapeng Mi
2026-10-29 4:51 ` sashiko-bot
2026-10-29 4:39 ` [Patch v5 08/18] perf/x86/intel: Avoid re-enabling PMU and LBR for BPF when disabled Dapeng Mi
2026-10-29 5:02 ` sashiko-bot
2026-10-29 4:39 ` [Patch v5 09/18] perf/x86/intel: Keep LBR frozen throughout PMI handling Dapeng Mi
2026-10-29 4:59 ` sashiko-bot
2026-10-29 10:29 ` Peter Zijlstra
2026-10-29 4:39 ` [Patch v5 10/18] perf/x86/intel: Allow LBR read helpers to operate on explicit stacks Dapeng Mi
2026-10-29 4:58 ` sashiko-bot
2026-10-29 10:38 ` Peter Zijlstra
2026-10-29 4:39 ` [Patch v5 11/18] perf/x86/intel: Use a dedicated LBR stack for BPF snapshotting Dapeng Mi
2026-10-29 5:05 ` sashiko-bot
2026-10-29 10:41 ` Peter Zijlstra
2026-10-29 4:39 ` [Patch v5 12/18] perf/x86/intel: Always snapshot live hardware LBR state for BPF Dapeng Mi
2026-10-29 5:01 ` sashiko-bot
2026-10-29 10:56 ` Peter Zijlstra
2026-10-29 4:39 ` [Patch v5 13/18] perf/x86/intel: Refresh LBR stack for non-PEBS LBR events if needed Dapeng Mi
2026-10-29 5:09 ` sashiko-bot
2026-10-29 11:00 ` Peter Zijlstra
2026-10-29 4:39 ` [Patch v5 14/18] perf/x86/intel: Account arch-PEBS in lbr_pebs_users Dapeng Mi
2026-10-29 4:55 ` sashiko-bot
2026-10-29 4:39 ` [Patch v5 15/18] perf/x86/intel: Clear raw LBR counters in the LBR stack Dapeng Mi
2026-10-29 5:03 ` sashiko-bot
2026-10-29 4:39 ` [Patch v5 16/18] perf/x86/intel: Refill LBR stack for LBR counter events in PMI handler Dapeng Mi
2026-10-29 5:16 ` sashiko-bot
2026-10-29 4:39 ` [Patch v5 17/18] perf/x86/intel: Pass LBR stack size into store_lbr() Dapeng Mi
2026-10-29 4:53 ` sashiko-bot
2026-10-29 4:39 ` [Patch v5 18/18] perf/core: Don't overwrite shared LBR stack depth Dapeng Mi
2026-10-29 4:57 ` sashiko-bot
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