* Peter Zijlstra <a.p.zijls...@chello.nl> wrote:
> On Wed, 2012-09-05 at 08:35 +0200, Ingo Molnar wrote:
> > * Yan, Zheng <zheng.z....@intel.com> wrote:
> >
> > > From: "Yan, Zheng" <zheng.z....@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....@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?
>
> No, part of the uncore PMUs are in MSR space and aren't
> discoverable. CPUID model checks + hard assumptions of
> presence are all that we are left with.
>
> Now Avi suggested we teach KVM about these MSRs and then
> modify the uncore driver to test if the MSRs actually work --
> as in retain values written to them and aren't always 0.
>
> That's a larger patch though, partly because enumerating the
> gazillion MSRs consumed by the various uncore PMUs is a
> tedious job, and we can always do this later.
>
> This patch is a minimal patch to at least make things 'work'
> for now.
Ok, no objections.
Thanks,
Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
