From: Sean Christopherson <seanjc@google.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>,
x86@kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Like Xu <like.xu@linux.intel.com>,
Dmitry Vyukov <dvyukov@google.com>,
syzbot+cce9ef2dd25246f815ee@syzkaller.appspotmail.com
Subject: Re: [PATCH v2] x86/perf: Use RET0 as default for guest_get_msrs to handle "no PMU" case
Date: Wed, 10 Mar 2021 10:16:00 -0800 [thread overview]
Message-ID: <YEkM4HWqjMdPoXvR@google.com> (raw)
In-Reply-To: <YEiA3hoCTMJbhKXO@hirez.programming.kicks-ass.net>
On Wed, Mar 10, 2021, Peter Zijlstra wrote:
> On Tue, Mar 09, 2021 at 09:10:19AM -0800, Sean Christopherson wrote:
>
> > @@ -2024,9 +2021,6 @@ static int __init init_hw_perf_events(void)
> > if (!x86_pmu.read)
> > x86_pmu.read = _x86_pmu_read;
> >
> > - if (!x86_pmu.guest_get_msrs)
> > - x86_pmu.guest_get_msrs = perf_guest_get_msrs_nop;
>
> I suspect I might've been over eager here and we're now in trouble when
> *_pmu_init() clears x86_pmu.guest_get_msrs (like for instance on AMD).
>
> When that happens we need to restore __static_call_return0, otherwise
> the following static_call_update() will patch in a NOP and RAX will be
> garbage again.
>
> So I've taken the liberty to update the patch as below.
Doh, I managed to forget about that between v1 and v2, too. Thanks much!
next prev parent reply other threads:[~2021-03-10 18:17 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-09 17:10 [PATCH v2] x86/perf: Use RET0 as default for guest_get_msrs to handle "no PMU" case Sean Christopherson
2021-03-09 18:26 ` Jim Mattson
[not found] ` <CALMp9eRL4QRq4-DKEveNsJ8b2XSYEhZ-zKGFWsCcoZMnDeRtxg@mail.gmail.com>
2021-03-09 19:46 ` Sean Christopherson
2021-03-10 8:18 ` Peter Zijlstra
2021-03-10 18:16 ` Sean Christopherson [this message]
2021-03-11 9:08 ` [tip: perf/urgent] " tip-bot2 for Sean Christopherson
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