From: Peter Zijlstra <peterz@infradead.org>
To: "Xu, Like" <like.xu@intel.com>
Cc: Sean Christopherson <seanjc@google.com>,
Dmitry Vyukov <dvyukov@google.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>,
linux-kernel@vger.kernel.org, Like Xu <like.xu@linux.intel.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Jim Mattson <jmattson@google.com>,
kvm@vger.kernel.org,
"Thomas Gleixner
(x86/pti/timer/core/smp/irq/perf/efi/locking/ras/objtool)
(x86@kernel.org)" <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Ingo Molnar <mingo@redhat.com>
Subject: Re: [PATCH] x86/perf: Fix guest_get_msrs static call if there is no PMU
Date: Mon, 8 Mar 2021 09:53:52 +0100 [thread overview]
Message-ID: <YEXmILSHDNDuMk/N@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <053d0a22-394d-90d0-8d3b-3cd37ca3f378@intel.com>
On Mon, Mar 08, 2021 at 10:25:59AM +0800, Xu, Like wrote:
> On 2021/3/6 6:33, Sean Christopherson wrote:
> > Handle a NULL x86_pmu.guest_get_msrs at invocation instead of patching
> > in perf_guest_get_msrs_nop() during setup. If there is no PMU, setup
>
> "If there is no PMU" ...
Then you shouldn't be calling this either ofcourse :-)
> > @@ -671,7 +671,11 @@ void x86_pmu_disable_all(void)
> > struct perf_guest_switch_msr *perf_guest_get_msrs(int *nr)
> > {
> > - return static_call(x86_pmu_guest_get_msrs)(nr);
> > + if (x86_pmu.guest_get_msrs)
> > + return static_call(x86_pmu_guest_get_msrs)(nr);
>
> How about using "static_call_cond" per commit "452cddbff7" ?
Given the one user in atomic_switch_perf_msrs() that should work because
it doesn't seem to care about nr_msrs when !msrs.
Still, it calling atomic_switch_perf_msrs() and
intel_pmu_lbr_is_enabled() when there isn't a PMU at all is of course, a
complete waste of cycles.
next prev parent reply other threads:[~2021-03-08 8:55 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-05 22:33 [PATCH] x86/perf: Fix guest_get_msrs static call if there is no PMU Sean Christopherson
2021-03-08 2:25 ` Xu, Like
2021-03-08 7:12 ` Dmitry Vyukov
2021-03-08 8:35 ` Like Xu
2021-03-08 8:51 ` Dmitry Vyukov
2021-03-08 8:53 ` Peter Zijlstra [this message]
2021-03-08 12:01 ` Xu, Like
2021-03-08 20:40 ` Sean Christopherson
2021-03-09 7:46 ` Peter Zijlstra
2021-03-09 8:45 ` Peter Zijlstra
2021-03-09 17:05 ` Sean Christopherson
2021-03-09 17:07 ` Dmitry Vyukov
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