Re: [RFC PATCH 13/13] KVM: SVM: Use fastpath x2apic IPI emulation when #vmexit with x2AVIC

[Suthikulpanit, Suravee]

Maxim,

On 2/25/2022 3:12 AM, Maxim Levitsky wrote:
> On Sun, 2022-02-20 at 20:19 -0600, Suravee Suthikulpanit wrote:
> > When sends IPI to a halting vCPU, the hardware generates
> > avic_incomplete_ipi #vmexit with the
> > AVIC_IPI_FAILURE_TARGET_NOT_RUNNING reason.
> >
> > For x2AVIC, enable fastpath emulation.
> >
> > Signed-off-by: Suravee Suthikulpanit<suravee.suthikulpanit@xxxxxxx>
> > ---
> >   arch/x86/kvm/svm/avic.c | 2 ++
> >   arch/x86/kvm/x86.c      | 3 ++-
> >   arch/x86/kvm/x86.h      | 1 +
> >   3 files changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
> > index 874c89f8fd47..758a79ee7f99 100644
> > --- a/arch/x86/kvm/svm/avic.c
> > +++ b/arch/x86/kvm/svm/avic.c
> > @@ -428,6 +428,8 @@ int avic_incomplete_ipi_interception(struct kvm_vcpu *vcpu)
> >   		kvm_lapic_reg_write(apic, APIC_ICR, icrl);
> >   		break;
> >   	case AVIC_IPI_FAILURE_TARGET_NOT_RUNNING:
> > +		handle_fastpath_set_x2apic_icr_irqoff(vcpu, svm->vmcb->control.exit_info_1);
> This just doesn't seem right - it sends IPI to the target, while we just need to wake it up.
> avic_kick_target_vcpus already does all of this, and it really should be optimized to avoid
> going over all vcpus as it does currently.

Ah, you are right. I'll remove this patch.

Regards,
Suravee