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    SubjectRe: [PATCH RESEND] KVM: Boosting vCPUs that are delivering interrupts
    On Thu, 18 Jul 2019 at 16:34, Paolo Bonzini <pbonzini@redhat.com> wrote:
    >
    > On 18/07/19 10:15, Christian Borntraeger wrote:
    > >
    > >
    > > On 18.07.19 09:59, Paolo Bonzini wrote:
    > >> On 12/07/19 09:15, Wanpeng Li wrote:
    > >>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
    > >>> index b4ab59d..2c46705 100644
    > >>> --- a/virt/kvm/kvm_main.c
    > >>> +++ b/virt/kvm/kvm_main.c
    > >>> @@ -2404,8 +2404,10 @@ void kvm_vcpu_kick(struct kvm_vcpu *vcpu)
    > >>> int me;
    > >>> int cpu = vcpu->cpu;
    > >>>
    > >>> - if (kvm_vcpu_wake_up(vcpu))
    > >>> + if (kvm_vcpu_wake_up(vcpu)) {
    > >>> + vcpu->preempted = true;
    > >>> return;
    > >>> + }
    > >>>
    > >>> me = get_cpu();
    > >>> if (cpu != me && (unsigned)cpu < nr_cpu_ids && cpu_online(cpu))
    > >>>
    > >>
    > >> Who is resetting vcpu->preempted to false in this case? This also
    > >> applies to s390 in fact.
    > >
    > > Isnt that done by the sched_in handler?
    >
    > I am a bit confused because, if it is done by the sched_in later, I
    > don't understand why the sched_out handler hasn't set vcpu->preempted
    > already.
    >
    > The s390 commit message is not very clear, but it talks about "a former
    > sleeping cpu" that "gave up the cpu voluntarily". Does "voluntarily"
    > that mean it is in kvm_vcpu_block? But then at least for x86 it would

    see the prepare_to_swait_exlusive() in kvm_vcpu_block(), the task will
    be set in TASK_INTERRUPTIBLE state, kvm_sched_out will set
    vcpu->preempted to true iff current->state == TASK_RUNNING.

    Regards,
    Wanpeng Li

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