From: Sean Christopherson <seanjc@google.com>
To: Colton Lewis <coltonlewis@google.com>
Cc: kvm@vger.kernel.org, Oliver Upton <oliver.upton@linux.dev>,
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>,
Kan Liang <kan.liang@linux.intel.com>,
Will Deacon <will@kernel.org>,
Russell King <linux@armlinux.org.uk>,
Catalin Marinas <catalin.marinas@arm.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Nicholas Piggin <npiggin@gmail.com>,
Christophe Leroy <christophe.leroy@csgroup.eu>,
Naveen N Rao <naveen@kernel.org>,
Heiko Carstens <hca@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Alexander Gordeev <agordeev@linux.ibm.com>,
Christian Borntraeger <borntraeger@linux.ibm.com>,
Sven Schnelle <svens@linux.ibm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org
Subject: Re: [PATCH v2 5/5] perf: Correct perf sampling with guest VMs
Date: Wed, 11 Sep 2024 15:56:19 -0700 [thread overview]
Message-ID: <ZuIgE2-GElzSGztH@google.com> (raw)
In-Reply-To: <20240911222433.3415301-6-coltonlewis@google.com>
On Wed, Sep 11, 2024, Colton Lewis wrote:
> Previously any PMU overflow interrupt that fired while a VCPU was
> loaded was recorded as a guest event whether it truly was or not. This
> resulted in nonsense perf recordings that did not honor
> perf_event_attr.exclude_guest and recorded guest IPs where it should
> have recorded host IPs.
>
> Rework the sampling logic to only record guest samples for events with
> exclude_guest clear. This way any host-only events with exclude_guest
> set will never see unexpected guest samples. The behaviour of events
> with exclude_guest clear is unchanged.
Nit, "with exclude_guest clear" is easy to misread as simply "with exclude_guest"
(I did so at least three times). Maybe
The behavior of exclude_guest=0 events is unchanged.
or
The behavior of events without exclude_guest is unchanged.
I think it's also worth explicitly calling out that events that are configured
to sample both host and guest may still be prone to misattributing a PMI that
arrived in the host as a guest event, depending on the KVM arch and/or vendor
behavior.
next prev parent reply other threads:[~2024-09-11 22:56 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-11 22:24 [PATCH v2 0/5] Correct perf sampling with Guest VMs Colton Lewis
2024-09-11 22:24 ` [PATCH v2 1/5] arm: perf: Drop unused functions Colton Lewis
2024-09-11 22:24 ` [PATCH v2 2/5] perf: Hoist perf_instruction_pointer() and perf_misc_flags() Colton Lewis
2024-09-11 22:24 ` [PATCH v2 3/5] powerpc: perf: Use perf_arch_instruction_pointer() Colton Lewis
2024-09-11 22:24 ` [PATCH v2 4/5] x86: perf: Refactor misc flag assignments Colton Lewis
2024-09-11 22:24 ` [PATCH v2 5/5] perf: Correct perf sampling with guest VMs Colton Lewis
2024-09-11 22:56 ` Sean Christopherson [this message]
2024-09-12 20:31 ` Colton Lewis
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