Re: [PATCH v2 8/9] KVM: return if kvm_vcpu_wake_up() did wake up the VCPU

Andrew Jones
2017-04-27T11:41:16Z

On Wed, Apr 26, 2017 at 10:32:26PM +0200, Radim Krčmář wrote:
> No need to kick a VCPU that we have just woken up.
>
> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
> ---
> include/linux/kvm_host.h | 2 +-
> virt/kvm/kvm_main.c | 12 ++++++++----
> 2 files changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 955debd82cf2..38cfe372918c 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -698,7 +698,7 @@ void kvm_vcpu_mark_page_dirty(struct kvm_vcpu *vcpu, gfn_t gfn);
> void kvm_vcpu_block(struct kvm_vcpu *vcpu);
> void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu);
> void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu);
> -void kvm_vcpu_wake_up(struct kvm_vcpu *vcpu);
> +bool kvm_vcpu_wake_up(struct kvm_vcpu *vcpu);
> void kvm_vcpu_kick(struct kvm_vcpu *vcpu);
> int kvm_vcpu_yield_to(struct kvm_vcpu *target);
> void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu);
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 1efb07643035..632f7b3e198c 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -183,8 +183,8 @@ bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req)
> kvm_make_request(req, vcpu);
> cpu = vcpu->cpu;
>
> - if (!(req & KVM_REQUEST_NO_WAKEUP))
> - kvm_vcpu_wake_up(vcpu);
> + if (!(req & KVM_REQUEST_NO_WAKEUP) && kvm_vcpu_wake_up(vcpu))
> + continue;
>
> if (cpus != NULL && cpu != -1 && cpu != me &&
> kvm_vcpu_exiting_guest_mode(vcpu) != OUTSIDE_GUEST_MODE)
> @@ -2195,7 +2195,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
> }
> EXPORT_SYMBOL_GPL(kvm_vcpu_block);
>
> -void kvm_vcpu_wake_up(struct kvm_vcpu *vcpu)
> +bool kvm_vcpu_wake_up(struct kvm_vcpu *vcpu)
> {
> struct swait_queue_head *wqp;
>
> @@ -2203,8 +2203,10 @@ void kvm_vcpu_wake_up(struct kvm_vcpu *vcpu)
> if (swait_active(wqp)) {
> swake_up(wqp);
> ++vcpu->stat.halt_wakeup;
> + return true;
> }
>
> + return false;
> }
> EXPORT_SYMBOL_GPL(kvm_vcpu_wake_up);
>
> @@ -2216,7 +2218,9 @@ void kvm_vcpu_kick(struct kvm_vcpu *vcpu)
> int me;
> int cpu = vcpu->cpu;
>
> - kvm_vcpu_wake_up(vcpu);
> + if (kvm_vcpu_wake_up(vcpu))
> + return;
> +
> me = get_cpu();
> if (cpu != me && (unsigned)cpu < nr_cpu_ids && cpu_online(cpu))
> if (kvm_arch_vcpu_should_kick(vcpu))
> --
> 2.12.2
>

Reviewed-by: Andrew Jones <drjones@redhat.com>