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SubjectRe: [PART1 RFC 5/9] svm: Add VMEXIT handlers for AVIC
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On 18/02/2016 17:27, Radim Krčmář wrote:
> 2016-02-18 16:53+0100, Paolo Bonzini:
>> Patch 9 is okay, but it is also necessary to clear IsRunning in
>> kvm_arch_vcpu_blocking and set it in kvm_arch_vcpu_unblocking. In
>> addition, vcpu_put/vcpu_load should not modify IsRunning between
>> kvm_arch_vcpu_blocking and kvm_arch_vcpu_unblocking. Do you agree?
>
> Yes.
>
> I think we don't need to clear IsRunning on preemption, which would
> simplify the protection. (I haven't thought much about userspace exit,
> so maybe we could skip that one as well, but we don't need to now.)
>
> The reason for that is that KVM knows that the VCPU was scheduled out,
> so it couldn't do much in the AVIC VMEXIT.
> (KVM could force scheduler to pritioritize the VCPU, but our kick
> doesn't do that now and it seems like a bad idea.)
>
> Does it seem reasonable?

Yes, and in fact it wouldn't need to clear and set IsRunning on
vcpu_put/vcpu_load; only on vcpu_blocking/vcpu_unblocking.

The IsRunning flag is more of a IsNotHalted flag, in the end.

Paolo

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