Messages in this thread | | | Date | Wed, 5 Sep 2012 20:52:33 +0200 | From | Andi Kleen <> | Subject | Re: [PATCH] perf/x86: Disable uncore on virtualized CPU. |
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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
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