Messages in this thread | | | Date | Thu, 15 Apr 2010 11:05:33 +0300 | From | Avi Kivity <> | Subject | Re: [PATCH V3] perf & kvm: Enhance perf to collect KVM guest os statistics from host side |
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On 04/15/2030 04:04 AM, Zhang, Yanmin wrote: > >> An even more accurate way to determine this is to check whether the >> interrupt frame points back at the 'int $2' instruction. However we >> plan to switch to a self-IPI method to inject the NMI, and I'm not sure >> wether APIC NMIs are accepted on an instruction boundary or whether >> there's some latency involved. >> > Yes. But the frame pointer checking seems a little complicated. >
An even bigger disadvantage is that it won't work with Sheng's patch, self-NMIs are not synchronous.
>>> trace_kvm_entry(vcpu->vcpu_id); >>> + >>> + percpu_write(current_vcpu, vcpu); >>> kvm_x86_ops->run(vcpu); >>> + percpu_write(current_vcpu, NULL); >>> >>> >> If you move this around the 'int $2' instructions you will close the >> race, as a stray NMI won't catch us updating the rip cache. But that >> depends on whether self-IPI is accepted on the next instruction or not. >> > Right. The kernel part has dependency on the self-IPI implementation. > I will move above percpu_write(current_vcpu, vcpu) (or a new wrapper function) > just around 'int $2'. > >
Or create a new function to inject the interrupt in x86.c. That will reduce duplication between svm.c and vmx.c.
> Sheng would find a solution on the self-IPI delivery. Let's separate my patch > and self-IPI as 2 issues as we don't know when the self-IPI delivery would be > resolved. >
Sure.
-- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.
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