From: Andi Kleen <andi@firstfloor.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: "Yan, Zheng" <zheng.z.yan@intel.com>,
a.p.zijlstra@chello.nl, eranian@google.com, mingo@elte.hu,
andi@firstfloor.org, avi@redhat.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] perf/x86: Disable uncore on virtualized CPU.
Date: Wed, 5 Sep 2012 20:52:33 +0200 [thread overview]
Message-ID: <20120905185233.GD16230@one.firstfloor.org> (raw)
In-Reply-To: <20120905063524.GA20710@gmail.com>
On Wed, Sep 05, 2012 at 08:35:24AM +0200, Ingo Molnar wrote:
>
> * Yan, Zheng <zheng.z.yan@intel.com> wrote:
>
> > From: "Yan, Zheng" <zheng.z.yan@intel.com>
> >
> > Initializing uncore PMU on virtualized CPU may hang the kernel.
> > This is because kvm does not emulate the entire hardware. Thers
> > are lots of uncore related MSRs, making kvm enumerate them all
> > is a non-trival task. So just disable uncore on virtualized CPU.
> >
> > Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
> > ---
> > arch/x86/kernel/cpu/perf_event_intel_uncore.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/arch/x86/kernel/cpu/perf_event_intel_uncore.c b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
> > index 0a55710..2f005ba 100644
> > --- a/arch/x86/kernel/cpu/perf_event_intel_uncore.c
> > +++ b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
> > @@ -2898,6 +2898,9 @@ static int __init intel_uncore_init(void)
> > if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
> > return -ENODEV;
> >
> > + if (cpu_has_hypervisor)
> > + return -ENODEV;
> > +
> > ret = uncore_pci_init();
> > if (ret)
> > goto fail;
>
> Cannot the presence of the uncore hardware be detected in a
> cleaner fashion, via the PCI config space and such?
Probably just by reading the registers and see that they are 0 and
when writing read back and check.
And the code should not hang when that happens, then this check wouldn't
be needed.
-Andi
next prev parent reply other threads:[~2012-09-05 18:52 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-21 9:08 [PATCH] perf/x86: Disable uncore on virtualized CPU Yan, Zheng
2012-08-21 12:55 ` Pekka Enberg
2012-08-31 7:12 ` Pekka Enberg
2012-08-21 14:31 ` Andi Kleen
2012-08-21 14:42 ` Pekka Enberg
2012-09-05 6:35 ` Ingo Molnar
2012-09-05 8:47 ` Peter Zijlstra
2012-09-05 9:08 ` Ingo Molnar
2012-09-05 18:52 ` Andi Kleen [this message]
2012-10-20 8:23 ` [tip:perf/urgent] perf/x86: Disable uncore on virtualized CPUs tip-bot for Yan, Zheng
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