Re: [PATCH] svm/avic: Do not send AVIC doorbell to self

["Suthikulpanit, Suravee" <Suravee.Suthikulpanit@amd.com>]

Alex,

On 5/7/2019 8:16 AM, Graf, Alexander wrote:
> [CAUTION: External Email]
> 
> On 03.05.19 15:38, Suthikulpanit, Suravee wrote:
>> AVIC doorbell is used to notify a running vCPU that interrupts
>> has been injected into the vCPU AVIC backing page. Current logic
>> checks only if a VCPU is running before sending a doorbell.
>> However, the doorbell is not necessary if the destination
>> CPU is itself.
>>
>> Add logic to check currently running CPU before sending doorbell.
>>
>> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
> 
> Reviewed-by: Alexander Graf <graf@amazon.com>

Thanks.

>> ---
>>   arch/x86/kvm/svm.c | 11 +++++++----
>>   1 file changed, 7 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
>> index 122788f..4bbf6fc 100644
>> --- a/arch/x86/kvm/svm.c
>> +++ b/arch/x86/kvm/svm.c
>> @@ -5283,10 +5283,13 @@ static void svm_deliver_avic_intr(struct kvm_vcpu *vcpu, int vec)
>>       kvm_lapic_set_irr(vec, vcpu->arch.apic);
>>       smp_mb__after_atomic();
>>
>> -     if (avic_vcpu_is_running(vcpu))
>> -             wrmsrl(SVM_AVIC_DOORBELL,
>> -                    kvm_cpu_get_apicid(vcpu->cpu));
>> -     else
>> +     if (avic_vcpu_is_running(vcpu)) { > +           int cpuid = vcpu->cpu;
>> +
>> +             if (cpuid != get_cpu())
> 
> Tiny nitpick: What would keep you from checking vcpu->cpu directly here?

Nothing. Just coding style.

Thanks,
Suravee