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. Paolo
