On Thu, 18 Jul 2019 at 17:39, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > > On 18/07/19 11:29, Wanpeng Li wrote: > > On Thu, 18 Jul 2019 at 17:07, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > >> > >> On 18/07/19 10:43, Wanpeng Li wrote: > >>>>> 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. > >> > >> Ok, I was totally blind to that "if" around vcpu->preempted = true, it's > >> obvious now. > >> > >> I think we need two flags then, for example vcpu->preempted and vcpu->ready: > >> > >> - kvm_sched_out sets both of them to true iff current->state == TASK_RUNNING > >> > >> - kvm_vcpu_kick sets vcpu->ready to true > >> > >> - kvm_sched_in clears both of them > > ... and also kvm_vcpu_on_spin should check vcpu->ready. vcpu->preempted > remains only for use by vmx_vcpu_pi_put. Done in v2, please have a look. :) Regards, Wanpeng Li
