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    SubjectRe: [PATCH v2] KVM: LAPIC: Per vCPU control over kvm_can_post_timer_interrupt
    On Tue, 7 Dec 2021 23:23:03 +0000
    Sean Christopherson <seanjc@google.com> wrote:

    >
    > static bool kvm_can_post_timer_interrupt(struct kvm_vcpu *vcpu)
    > {
    > - return pi_inject_timer && kvm_vcpu_apicv_active(vcpu);
    > + return pi_inject_timer && kvm_vcpu_apicv_active(vcpu) &&
    > + (kvm_mwait_in_guest(vcpu) || kvm_hlt_in_guest(vcpu));
    > }
    >
    > bool kvm_can_use_hv_timer(struct kvm_vcpu *vcpu)
    > {
    > - return kvm_x86_ops.set_hv_timer
    > - && !(kvm_mwait_in_guest(vcpu->kvm) ||
    > - kvm_can_post_timer_interrupt(vcpu));
    > + /*
    > + * Don't use the hypervisor timer, a.k.a. VMX Preemption Timer, if the
    > + * guest can execute MWAIT without exiting as the timer will stop
    > + * counting if the core enters C3 or lower. HLT in the guest is ok as
    > + * HLT is effectively C1 and the timer counts in C0, C1, and C2.
    > + *
    > + * Don't use the hypervisor timer if KVM can post a timer interrupt to
    > + * the guest since posted the timer avoids taking an extra a VM-Exit
    > + * when the timer expires.
    > + */
    > + return kvm_x86_ops.set_hv_timer &&
    > + !kvm_mwait_in_guest(vcpu->kvm) &&
    > + !kvm_can_post_timer_interrupt(vcpu));
    > }
    > EXPORT_SYMBOL_GPL(kvm_can_use_hv_timer);
    >

    Sorry, I am little confused here now:
    if kvm_can_post_timer_interrupt(vcpu) return true(cpu-pm enabled), then the kvm_can_use_hv_timer will always be false;
    if kvm_can_post_timer_interrupt(vcpu) return false(cpu-pm disable),then kvm_mwait_in_guest(vcpu->kvm) can't be true ether;
    It seems we don't need kvm_mwait_in_guest(vcpu->kvm) here?

    Sorry, I am just a little confused and not too sure about this, if anything wrong, just ignore it.

    Thanks!

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      Last update: 2021-12-08 11:22    [W:4.348 / U:0.008 seconds]
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