On 27/04/2017 14:06, Cornelia Huck wrote: > On Wed, 26 Apr 2017 22:32:23 +0200 > Radim Krčmář <rkrcmar@xxxxxxxxxx> wrote: > >> We want to have kvm_make_all_cpus_request() to be an optmized version of >> >> kvm_for_each_vcpu(i, vcpu, kvm) { >> kvm_make_request(vcpu, request); >> kvm_vcpu_kick(vcpu); >> } >> >> and kvm_vcpu_kick() wakes up the target vcpu. We know which requests do >> not need the wake up and use it to optimize the loop. >> >> Thanks to that, this patch doesn't change the behavior of current users >> (the all don't need the wake up) and only prepares for future where the > > s/the all/they all/ > >> wake up is going to be needed. >> >> I think that most requests do not need the wake up, so we would flip the >> bit then. >> >> kvm_vcpu_kick() will get this condition after it is merged with >> kvm_make_request() because we currently don't know which request is being >> kicked. > > I find this sentence confusing: not all kicks are directly related to > requests. I agree, it is backwards. Changing to "Later on, kvm_make_request() will take care of kicking too, using this bit to make the decision whether to kick or not". Paolo >> >> Signed-off-by: Radim Krčmář <rkrcmar@xxxxxxxxxx> >> --- >> virt/kvm/kvm_main.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c >> index e5d52b46b531..3772f7dcc72d 100644 >> --- a/virt/kvm/kvm_main.c >> +++ b/virt/kvm/kvm_main.c >> @@ -186,6 +186,9 @@ bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req) >> /* Set ->requests bit before we read ->mode. */ >> smp_mb__after_atomic(); >> >> + if (!(req & KVM_REQUEST_NO_WAKEUP)) >> + kvm_vcpu_wake_up(vcpu); >> + >> if (cpus != NULL && cpu != -1 && cpu != me && >> kvm_vcpu_exiting_guest_mode(vcpu) != OUTSIDE_GUEST_MODE) >> cpumask_set_cpu(cpu, cpus); > > The code change looks good to me. >