linux-kernel - Re: [PATCH] x86/perf: Fix guest_get_msrs static call if there is no PMU

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Message-ID: <CACT4Y+b6rDO0PiHrhYHMynXmW+f_s5AaJLDo39rGJX69ZWSaMQ@mail.gmail.com>
Date:   Tue, 9 Mar 2021 18:07:14 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        "Xu, Like" <like.xu@...el.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Like Xu <like.xu@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        KVM list <kvm@...r.kernel.org>,
        "Thomas Gleixner
        (x86/pti/timer/core/smp/irq/perf/efi/locking/ras/objtool)
        (x86@...nel.org)" <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH] x86/perf: Fix guest_get_msrs static call if there is no PMU

On Tue, Mar 9, 2021 at 6:05 PM Sean Christopherson <seanjc@...gle.com> wrote:
>
> On Tue, Mar 09, 2021, Peter Zijlstra wrote:
> > On Tue, Mar 09, 2021 at 08:46:49AM +0100, Peter Zijlstra wrote:
> > > On Mon, Mar 08, 2021 at 12:40:44PM -0800, Sean Christopherson wrote:
> > > > On Mon, Mar 08, 2021, Peter Zijlstra wrote:
> > >
> > > > > Given the one user in atomic_switch_perf_msrs() that should work because
> > > > > it doesn't seem to care about nr_msrs when !msrs.
> > > >
> > > > Uh, that commit quite cleary says:
> > >
> > > D0h! I got static_call_cond() and __static_call_return0 mixed up.
> > > Anyway, let me see if I can make something work here.
> >
> > Does this work? I can never seem to start a VM, and if I do accidentally
> > manage, then it never contains the things I need :/
>
> Yep, once I found the dependencies in tip/sched/core (thank tip-bot!).  I'll
> send v2 your way.

If you are resending, please also add the syzbot Reported-by tag. Thanks.