Re: [PATCH V3] perf & kvm: Enhance perf to collect KVM guest os statisticsfrom host side

[Avi Kivity]

On 04/15/2010 12:44 PM, oerg Roedel wrote:
> > So, we'd need something like the following:
> >
> >     if (exit == NMI)
> >         __get_cpu_var(nmi_vcpu) = vcpu;
> >
> >     stgi();
> >
> >     if (exit == NMI) {
> >         while (!nmi_handled())
> >             cpu_relax();
> >         __get_cpu_var(nmi_vcpu) = NULL;
> >     }
> >      
> Hmm, looks a bit complicated to me. The NMI should happen shortly after
> the stgi instruction. Interrupts are still disabled so we stay on this
> cpu. Can't we just set and erase the cpu_var at vcpu_load/vcpu_put time?
>
>    

That means an NMI that happens outside guest code (for example, in the 
mmu, or during the exit itself) would be counted as if in guest code.

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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