On Fri, 2021-10-08 at 19:11 -0700, Sean Christopherson wrote:
> Add a comment to document that halt-polling is considered successful even
> if the polling loop itself didn't detect a wake event, i.e. if a wake
> event was detect in the final kvm_vcpu_check_block(). Invert the param
> to update helper so that the helper is a dumb function that is "told"
> whether or not polling was successful, as opposed to determining success
> based on blocking behavior.
>
> Opportunistically tweak the params to the update helper to reduce the
> line length for the call site so that it fits on a single line, and so
> that the prototype conforms to the more traditional kernel style.
>
> No functional change intended.
>
> Reviewed-by: David Matlack <dmatlack@xxxxxxxxxx>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---
> virt/kvm/kvm_main.c | 20 +++++++++++++-------
> 1 file changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 6156719bcbbc..4dfcd736b274 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -3201,13 +3201,15 @@ static int kvm_vcpu_check_block(struct kvm_vcpu *vcpu)
> return ret;
> }
>
> -static inline void
> -update_halt_poll_stats(struct kvm_vcpu *vcpu, u64 poll_ns, bool waited)
> +static inline void update_halt_poll_stats(struct kvm_vcpu *vcpu, ktime_t start,
> + ktime_t end, bool success)
> {
> - if (waited)
> - vcpu->stat.generic.halt_poll_fail_ns += poll_ns;
> - else
> + u64 poll_ns = ktime_to_ns(ktime_sub(end, start));
> +
> + if (success)
> vcpu->stat.generic.halt_poll_success_ns += poll_ns;
> + else
> + vcpu->stat.generic.halt_poll_fail_ns += poll_ns;
> }
>
> /*
> @@ -3277,9 +3279,13 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
> kvm_arch_vcpu_unblocking(vcpu);
> block_ns = ktime_to_ns(cur) - ktime_to_ns(start);
>
> + /*
> + * Note, halt-polling is considered successful so long as the vCPU was
> + * never actually scheduled out, i.e. even if the wake event arrived
> + * after of the halt-polling loop itself, but before the full wait.
> + */
> if (do_halt_poll)
> - update_halt_poll_stats(
> - vcpu, ktime_to_ns(ktime_sub(poll_end, start)), waited);
> + update_halt_poll_stats(vcpu, start, poll_end, !waited);
>
> if (halt_poll_allowed) {
> if (!vcpu_valid_wakeup(vcpu)) {
Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
Best regards,
Maxim Levitsky
