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

Avi Kivity
2010-04-15T09:09:28Z

On 04/15/2010 12:04 PM, oerg Roedel wrote:
> On Mon, Apr 15, 2030 at 04:57:38PM +0800, Zhang, Yanmin wrote:
>
>
>> I checked svm.c and it seems svm.c doesn't trigger a NMI to host if the NMI
>> happens in guest os. In addition, svm_complete_interrupts is called after
>> interrupt is enabled.
>>
> Yes. The NMI is held pending by the hardware until the STGI instruction
> is executed.
> And for nested svm the svm_complete_interrupts function needs to be
> executed after the nested exit handling. Therefore it is done late on
> svm.
>

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;
}

and no code sharing betweem vmx and svm.

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