Re: [PART1 RFC v3 12/12] svm: Manage vcpu load/unload when enable AVIC

Radim Krčmář
2016-04-06T12:36:40Z

2016-04-06 10:40+0700, Suravee Suthikulpanit:
> On 04/05/2016 09:56 PM, Radim Krčmář wrote:
>>I meant to change the place where we remember that is_running must not
>>be true. Something like
>>
>> svm_vcpu_blocking(struct kvm_vcpu *vcpu):
>> vcpu->is_blocking = true;
>> avic_set_running(vcpu, false);
>>
>> avic_vcpu_load(struct kvm_vcpu *vcpu, bool is_load):
>> avic_set_running(vcpu, is_load && !vcpu->is_blocking)
>
> I assume that you also imply that we would also need:
>
> svm_vcpu_unblocking(struct kvm_vcpu *vcpu) {
> avic_set_running(vcpu, false);
> vcpu->is_blocking = false;
> }

Yes, thought the order should be flipped in order to avoid suboptimal
case when preemption hits us after avic_set_running().

static void svm_vcpu_unblocking(struct kvm_vcpu *vcpu) {
vcpu->is_blocking = false;
avic_set_running(vcpu, true);
}

avic_set_running has barriers that prevent GCC from harmful reordering.