Re: [RFC PATCH 06/13] KVM: SVM: Add logic to determine x2APIC mode

[Suravee Suthikulpanit]

Hi Maxim

On 2/25/22 12:29 AM, Maxim Levitsky wrote:
> > diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> > index 1a0bf6b853df..bfbebb933da2 100644
> > --- a/arch/x86/kvm/svm/svm.h
> > +++ b/arch/x86/kvm/svm/svm.h
> > @@ -225,6 +225,7 @@ struct vcpu_svm {
> >   	u32 dfr_reg;
> >   	struct page *avic_backing_page;
> >   	u64 *avic_physical_id_cache;
> > +	bool x2apic_enabled;
> >   
> >   	/*
> >   	 * Per-vcpu list of struct amd_svm_iommu_ir:
> > @@ -566,6 +567,7 @@ void avic_init_vmcb(struct vcpu_svm *svm);
> >   int avic_incomplete_ipi_interception(struct kvm_vcpu *vcpu);
> >   int avic_unaccelerated_access_interception(struct kvm_vcpu *vcpu);
> >   int avic_init_vcpu(struct vcpu_svm *svm);
> > +void avic_update_vapic_bar(struct vcpu_svm *svm, u64 data);
> >   void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu);
> >   void avic_vcpu_put(struct kvm_vcpu *vcpu);
> >   void avic_post_state_restore(struct kvm_vcpu *vcpu);
>
>  ....
>
> I also don't think you need x2apic_enabled boolean.
> You can already know if a vCPU uses apic or x2apic via
>
> kvm_get_apic_mode(vcpu);
>
> in fact I don't think avic code should have any bookeeping in regard to x2apic/x2avic mode,
> but rather kvm's apic mode  (which is read directly from apic base msr (vcpu->arch.apic_base),
> should enable avic, or x2avic if possible, or inhibit avic if not possible.
>
> e.g it should drive the bits in vmcb and such.

I'll also clean this up in V2.

Regards,
Suravee