[no idea if this change makes sense (and especially if it has any bad
side effects), do you have performance numbers? I'll just have a look at
the general structure of the patch in the meanwhile]
> +bool kvm_arch_vcpu_spin_kernmode(struct kvm_vcpu *vcpu)
kvm_arch_vcpu_in_kernel() ?
> +{
> + return kvm_x86_ops->get_cpl(vcpu) == 0;
> +}
> +
> int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
> {
> return kvm_vcpu_exiting_guest_mode(vcpu) == IN_GUEST_MODE;
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 648b34c..f8f0d74 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -272,6 +272,9 @@ struct kvm_vcpu {
> } spin_loop;
> #endif
> bool preempted;
> + /* If vcpu is in kernel-mode when preempted */
> + bool in_kernmode;
> +
Why do you have to store that ...
[...]> + me->in_kernmode = kvm_arch_vcpu_spin_kernmode(me);
> kvm_vcpu_set_in_spin_loop(me, true);
> /*
> * We boost the priority of a VCPU that is runnable but not
> @@ -2351,6 +2353,8 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
> continue;
> if (swait_active(&vcpu->wq) &&
> !kvm_arch_vcpu_runnable(vcpu))
> continue;
> + if (me->in_kernmode && !vcpu->in_kernmode)
Wouldn't it be easier to simply have
in_kernel = kvm_arch_vcpu_in_kernel(me);
...
if (in_kernel && !kvm_arch_vcpu_in_kernel(vcpu))
...
> + continue;
> if (!kvm_vcpu_eligible_for_directed_yield(vcpu))
> continue;
>
> @@ -4009,8 +4013,11 @@ static void kvm_sched_out(struct preempt_notifier *pn,
> {
> struct kvm_vcpu *vcpu = preempt_notifier_to_vcpu(pn);
>
> - if (current->state == TASK_RUNNING)
> + if (current->state == TASK_RUNNING) {
> vcpu->preempted = true;
> + vcpu->in_kernmode = kvm_arch_vcpu_spin_kernmode(vcpu);
> + }
> +
so you don't have to do this change, too.
> kvm_arch_vcpu_put(vcpu);
> }
>
>
--
Thanks,
David
