> Am 28.08.2019 um 17:19 schrieb Suthikulpanit, Suravee <Suravee.Suthikulpanit@xxxxxxx>:
>
> Alex,
>
>> On 8/19/19 5:35 AM, Alexander Graf wrote:
>>
>>
>>> On 15.08.19 18:25, Suthikulpanit, Suravee wrote:
>>> AMD AVIC does not support ExtINT. Therefore, AVIC must be temporary
>>> deactivated and fall back to using legacy interrupt injection via vINTR
>>> and interrupt window.
>>>
>>> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
>>> ---
>>> arch/x86/kvm/svm.c | 49
>>> +++++++++++++++++++++++++++++++++++++++++++++----
>>> 1 file changed, 45 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
>>> index cfa4b13..4690351 100644
>>> --- a/arch/x86/kvm/svm.c
>>> +++ b/arch/x86/kvm/svm.c
>>> @@ -384,6 +384,7 @@ struct amd_svm_iommu_ir {
>>> static void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0);
>>> static void svm_flush_tlb(struct kvm_vcpu *vcpu, bool invalidate_gpa);
>>> static void svm_complete_interrupts(struct vcpu_svm *svm);
>>> +static void svm_request_activate_avic(struct kvm_vcpu *vcpu);
>>> static bool svm_get_enable_apicv(struct kvm *kvm);
>>> static inline void avic_post_state_restore(struct kvm_vcpu *vcpu);
>>> @@ -4494,6 +4495,15 @@ static int interrupt_window_interception(struct
>>> vcpu_svm *svm)
>>> {
>>> kvm_make_request(KVM_REQ_EVENT, &svm->vcpu);
>>> svm_clear_vintr(svm);
>>> +
>>> + /*
>>> + * For AVIC, the only reason to end up here is ExtINTs.
>>> + * In this case AVIC was temporarily disabled for
>>> + * requesting the IRQ window and we have to re-enable it.
>>> + */
>>> + if (svm_get_enable_apicv(svm->vcpu.kvm))
>>> + svm_request_activate_avic(&svm->vcpu);
>>
>> Would it make sense to add a trace point here and to the other call
>> sites, so that it becomes obvious in a trace when and why exactly avic
>> was active/inactive?
>>
>> The trace point could add additional information on the why.
>
> Sure, sounds good.
>
>>> ....
>>> @@ -5522,9 +5558,6 @@ static void enable_irq_window(struct kvm_vcpu
>>> *vcpu)
>>> {
>>> struct vcpu_svm *svm = to_svm(vcpu);
>>> - if (kvm_vcpu_apicv_active(vcpu))
>>> - return;
>>> -
>>> /*
>>> * In case GIF=0 we can't rely on the CPU to tell us when GIF
>>> becomes
>>> * 1, because that's a separate STGI/VMRUN intercept. The next
>>> time we
>>> @@ -5534,6 +5567,14 @@ static void enable_irq_window(struct kvm_vcpu
>>> *vcpu)
>>> * window under the assumption that the hardware will set the GIF.
>>> */
>>> if ((vgif_enabled(svm) || gif_set(svm)) && nested_svm_intr(svm)) {
>>> + /*
>>> + * IRQ window is not needed when AVIC is enabled,
>>> + * unless we have pending ExtINT since it cannot be injected
>>> + * via AVIC. In such case, we need to temporarily disable AVIC,
>>> + * and fallback to injecting IRQ via V_IRQ.
>>> + */
>>> + if (kvm_vcpu_apicv_active(vcpu))
>>> + svm_request_deactivate_avic(&svm->vcpu);
>>
>> Did you test AVIC with nesting? Did you actually run across this issue
>> there?
>
> Currently, we have not claimed that AVIC is supported w/ nested VM.
> That's why we have not enabled AVIC by default yet. We will be looking
> more into that next.
If it's not supported, please suspend it when we enter a nested guest then? In that case, the above change is also unnecessary, as it only affects nested guests, no?
Alex
>
> Suravee
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