linux-kernel - Re: [PATCH] perf/core: fix the bug in the event multiplexing

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Message-ID: <ZNNYCQjsi30APZQ+@linux.dev>
Date:   Wed, 9 Aug 2023 09:10:33 +0000
From:   Oliver Upton <oliver.upton@...ux.dev>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Huang Shijie <shijie@...amperecomputing.com>, james.morse@....com,
        suzuki.poulose@....com, yuzenghui@...wei.com,
        catalin.marinas@....com, will@...nel.org, pbonzini@...hat.com,
        peterz@...radead.org, ingo@...hat.com, acme@...nel.org,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        jolsa@...nel.org, namhyung@...nel.org, irogers@...gle.com,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-perf-users@...r.kernel.org, patches@...erecomputing.com,
        zwang@...erecomputing.com
Subject: Re: [PATCH] perf/core: fix the bug in the event multiplexing

On Wed, Aug 09, 2023 at 09:48:29AM +0100, Marc Zyngier wrote:

[...]

> Another question is how the same thing is handled on x86? Maybe they
> don't suffer from this problem thanks to specific architectural
> features, but it'd be good to find out, as this may guide the
> implementation in a different way.

I'm pretty sure the bug here is arm64 specific. x86 (at least on intel)
fetches the guest PMU context from the perf driver w/ irqs disabled
immediately before entering the guest (see atomic_switch_perf_msrs()).

-- 
Thanks,
Oliver