From: Sandipan Das <sandipan.das@amd.com>
To: <linux-perf-users@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <bpf@vger.kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Namhyung Kim <namhyung@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
"Alexander Shishkin" <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@kernel.org>, Ian Rogers <irogers@google.com>,
Adrian Hunter <adrian.hunter@intel.com>,
James Clark <james.clark@linaro.org>,
Thomas Gleixner <tglx@kernel.org>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>, <x86@kernel.org>,
"H . Peter Anvin" <hpa@zytor.com>,
Dapeng Mi <dapeng1.mi@linux.intel.com>,
Andrii Nakryiko <andrii@kernel.org>, Song Liu <song@kernel.org>,
Ravi Bangoria <ravi.bangoria@amd.com>,
Ananth Narayan <ananth.narayan@amd.com>,
Sandipan Das <sandipan.das@amd.com>
Subject: [PATCH v2 0/2] perf/x86: Limit branch snapshots to valid entries
Date: Thu, 15 Oct 2026 17:16:10 +0530 [thread overview]
Message-ID: <cover.1792064123.git.sandipan.das@amd.com> (raw)
Sashiko reported that the vendor-specific branch snapshot callbacks
used by bpf_get_branch_snapshot() copy up to x86_pmu.lbr_nr entries
from cpuc->lbr_entries[], regardless of how many valid entries the
last LBR read produced. This makes BPF programs read stale or invalid
branch records. Patch 1 addresses AMD and patch 2 addresses Intel.
Previous version(s) can be found at
v1: https://lore.kernel.org/all/20261007181002.4005262-1-sandipan.das@amd.com/
Changes in v2:
* Include a fix for Intel LBR.
* Add Tested-by from Dapeng to the Intel fix.
https://lore.kernel.org/all/eb6c7bda-0dcf-4fac-ad69-9f5b24abc21b@linux.intel.com/
Sandipan Das (2):
perf/x86/amd/lbr: Limit branch snapshots to valid entries
perf/x86/intel/lbr: Limit branch snapshots to valid entries
arch/x86/events/amd/core.c | 2 +-
arch/x86/events/amd/lbr.c | 4 +++-
arch/x86/events/intel/core.c | 2 +-
arch/x86/events/intel/lbr.c | 4 +++-
4 files changed, 8 insertions(+), 4 deletions(-)
--
2.53.0
next reply other threads:[~2026-10-15 11:47 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-15 11:46 Sandipan Das [this message]
2026-10-15 11:46 ` [PATCH v2 1/2] perf/x86/amd/lbr: Limit branch snapshots to valid entries Sandipan Das
2026-10-15 12:01 ` sashiko-bot
2026-10-16 0:14 ` Mi, Dapeng
2026-10-15 11:46 ` [PATCH v2 2/2] perf/x86/intel/lbr: " Sandipan Das
2026-10-15 12:01 ` sashiko-bot
2026-10-16 0:14 ` Mi, Dapeng
2026-10-16 0:21 ` bot+bpf-ci
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