Re: [PART1 RFC v3 11/12] svm: Do not intercept CR8 when enable AVIC

Radim Krčmář
2016-03-18T21:10:57Z

2016-03-18 01:09-0500, Suravee Suthikulpanit:
> When enable AVIC:
> * Do not intercept CR8 since this should be handled by AVIC HW.
> * Also update TPR in APIC backing page when syncing CR8 before VMRUN
>
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
> ---
> arch/x86/kvm/svm.c | 15 +++++++++++----
> 1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index ba84d57..d5418c3 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -984,6 +984,8 @@ static __init int svm_hardware_setup(void)
>
> if (avic) {
> printk(KERN_INFO "kvm: AVIC enabled\n");
> +
> + svm_x86_ops.update_cr8_intercept = NULL;

This doesn't look right.

> } else {
> svm_x86_ops.deliver_posted_interrupt = NULL;
> }
> @@ -1097,7 +1099,8 @@ static void init_vmcb(struct vcpu_svm *svm)
> set_cr_intercept(svm, INTERCEPT_CR0_WRITE);
> set_cr_intercept(svm, INTERCEPT_CR3_WRITE);
> set_cr_intercept(svm, INTERCEPT_CR4_WRITE);
> - set_cr_intercept(svm, INTERCEPT_CR8_WRITE);
> + if (!svm_vcpu_avic_enabled(svm))
> + set_cr_intercept(svm, INTERCEPT_CR8_WRITE);
>
> set_dr_intercepts(svm);
>
> @@ -4080,7 +4083,8 @@ static void update_cr8_intercept(struct kvm_vcpu *vcpu, int tpr, int irr)
> {
> struct vcpu_svm *svm = to_svm(vcpu);
>
> - if (is_guest_mode(vcpu) && (vcpu->arch.hflags & HF_VINTR_MASK))
> + if ((is_guest_mode(vcpu) && (vcpu->arch.hflags & HF_VINTR_MASK)) ||
> + svm_vcpu_avic_enabled(svm))
> return;
>
> clr_cr_intercept(svm, INTERCEPT_CR8_WRITE);
> @@ -4271,9 +4275,12 @@ static inline void sync_lapic_to_cr8(struct kvm_vcpu *vcpu)
> if (is_guest_mode(vcpu) && (vcpu->arch.hflags & HF_VINTR_MASK))
> return;

I think we can exit early with svm_vcpu_avic_enabled().

>
> - cr8 = kvm_get_cr8(vcpu);
> + cr8 = kvm_get_cr8(vcpu) & V_TPR_MASK;
> svm->vmcb->control.int_ctl &= ~V_TPR_MASK;
> - svm->vmcb->control.int_ctl |= cr8 & V_TPR_MASK;
> + svm->vmcb->control.int_ctl |= cr8;
> +
> + if (svm_vcpu_avic_enabled(svm))
> + kvm_lapic_set_reg(svm->vcpu.arch.apic, APIC_TASKPRI, (u32)cr8 << 4);

kvm_get_cr8() == kvm_lapic_get_reg(APIC_TASKPRI) >> 4.

> }
>
> static void svm_complete_interrupts(struct vcpu_svm *svm)
> --
> 1.9.1
>