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 > > This way, vmx_vcpu_pi_load can keep looking at preempted only (it > handles voluntary preemption in pi_pre_block/pi_post_block). > > Also, kvm_s390_vcpu_wakeup can be changed to use kvm_vcpu_wake_up, which > is nice. Will do. :) Wanpeng
