From: Ravi Bangoria <ravi.bangoria@amd.com>
To: Liew Rui Yan <aethernet65535@gmail.com>
Cc: <linux-perf-users@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <x86@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Manali Shukla <manali.shukla@amd.com>,
Jim Mattson <jmattson@google.com>, 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>,
"H. Peter Anvin" <hpa@zytor.com>,
Ravi Bangoria <ravi.bangoria@amd.com>
Subject: Re: perf/amd/ibs: [BUG?] ibs_op sampling silently stops on Zen3: MSR_AMD64_IBSOPCTL latched, no NMI delivered
Date: Tue, 27 Oct 2026 10:53:22 +0530 [thread overview]
Message-ID: <ded8ef5a-8919-4063-815e-27fc38e4c204@amd.com> (raw)
In-Reply-To: <20261019212028.119312-1-aethernet65535@gmail.com>
> I found an issue with ibs_op sampling that I can reproduce on my AMD
> Zen3 laptop. Under full CPU load, sampling PMIs stop arriving on each
> CPU, one after another. Reading MSR_AMD64_IBSOPCTL (0xc0011033) while
> perf is still running shows the hardware has latched a completed sample
> (IBS_OP_ENABLE=1, IBS_OP_VAL=1, IBS_OP_CUR_CNT frozen) and is waiting
> for an NMI that never arrives. The CPU never recovers on its own.
>
> I am really not very familiar with CPU, so I would appreciate any
> guidance on whether this is known and what to test next.
This is a known Zen3 hardware bug. The workaround involves opening a
PMC event alongside the IBS event so that the IBS sample is acknowledged
during the PMC NMI, thereby resuming the stalled IBS instance.
More details in The Revision guide:
https://bugzilla.kernel.org/attachment.cgi?id=311307
Erratum 1285 Processor May Fail to Report IBS (Instruction Based
Sampling) Performance Sample
Thanks,
Ravi
prev parent reply other threads:[~2026-10-27 5:27 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-19 21:20 Liew Rui Yan
2026-10-27 5:23 ` Ravi Bangoria [this message]
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