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SubjectRe: [RFC PATCH v5 076/104] KVM: x86: Add option to force LAPIC expiration wait
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On 3/4/22 20:49, isaku.yamahata@intel.com wrote:
> From: Sean Christopherson <sean.j.christopherson@intel.com>
>
> Add an option to skip the IRR check-in kvm_wait_lapic_expire(). This
> will be used by TDX to wait if there is an outstanding notification for
> a TD, i.e. a virtual interrupt is being triggered via posted interrupt
> processing. KVM TDX doesn't emulate PI processing, i.e. there will
> never be a bit set in IRR/ISR, so the default behavior for APICv of
> querying the IRR doesn't work as intended.

Would be better to explain "doesn't work as intended" more verbosely.
Otherwise,

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

Paolo

> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> ---
> arch/x86/kvm/lapic.c | 4 ++--
> arch/x86/kvm/lapic.h | 2 +-
> arch/x86/kvm/svm/svm.c | 2 +-
> arch/x86/kvm/vmx/vmx.c | 2 +-
> 4 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 9322e6340a74..d49f029ef0e3 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1620,12 +1620,12 @@ static void __kvm_wait_lapic_expire(struct kvm_vcpu *vcpu)
> __wait_lapic_expire(vcpu, tsc_deadline - guest_tsc);
> }
>
> -void kvm_wait_lapic_expire(struct kvm_vcpu *vcpu)
> +void kvm_wait_lapic_expire(struct kvm_vcpu *vcpu, bool force_wait)
> {
> if (lapic_in_kernel(vcpu) &&
> vcpu->arch.apic->lapic_timer.expired_tscdeadline &&
> vcpu->arch.apic->lapic_timer.timer_advance_ns &&
> - lapic_timer_int_injected(vcpu))
> + (force_wait || lapic_timer_int_injected(vcpu)))
> __kvm_wait_lapic_expire(vcpu);
> }
> EXPORT_SYMBOL_GPL(kvm_wait_lapic_expire);
> diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
> index 2b44e533fc8d..2a0119ef9e96 100644
> --- a/arch/x86/kvm/lapic.h
> +++ b/arch/x86/kvm/lapic.h
> @@ -233,7 +233,7 @@ static inline int kvm_lapic_latched_init(struct kvm_vcpu *vcpu)
>
> bool kvm_apic_pending_eoi(struct kvm_vcpu *vcpu, int vector);
>
> -void kvm_wait_lapic_expire(struct kvm_vcpu *vcpu);
> +void kvm_wait_lapic_expire(struct kvm_vcpu *vcpu, bool force_wait);
>
> void kvm_bitmap_or_dest_vcpus(struct kvm *kvm, struct kvm_lapic_irq *irq,
> unsigned long *vcpu_bitmap);
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index c7eec23e9ebe..a46415845f48 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -3766,7 +3766,7 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu)
> clgi();
> kvm_load_guest_xsave_state(vcpu);
>
> - kvm_wait_lapic_expire(vcpu);
> + kvm_wait_lapic_expire(vcpu, false);
>
> /*
> * If this vCPU has touched SPEC_CTRL, restore the guest's value if
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 00f88aa25047..9b7bd52d19a9 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -6838,7 +6838,7 @@ fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
> if (enable_preemption_timer)
> vmx_update_hv_timer(vcpu);
>
> - kvm_wait_lapic_expire(vcpu);
> + kvm_wait_lapic_expire(vcpu, false);
>
> /*
> * If this vCPU has touched SPEC_CTRL, restore the guest's value if

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