On Mon, Nov 20, 2023 at 03:26:08PM +0100, Vitaly Kuznetsov wrote:
> Yury Norov <yury.norov@xxxxxxxxx> writes:
>
> > The function traverses stimer_pending_bitmap n a for-loop bit by bit.
> > We can do it faster by using atomic find_and_set_bit().
> >
> > While here, refactor the logic by decreasing indentation level
> > and dropping 2nd check for stimer->config.enable.
> >
> > Signed-off-by: Yury Norov <yury.norov@xxxxxxxxx>
> > ---
> > arch/x86/kvm/hyperv.c | 39 +++++++++++++++++++--------------------
> > 1 file changed, 19 insertions(+), 20 deletions(-)
> >
> > diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> > index 238afd7335e4..460e300b558b 100644
> > --- a/arch/x86/kvm/hyperv.c
> > +++ b/arch/x86/kvm/hyperv.c
> > @@ -870,27 +870,26 @@ void kvm_hv_process_stimers(struct kvm_vcpu *vcpu)
> > if (!hv_vcpu)
> > return;
> >
> > - for (i = 0; i < ARRAY_SIZE(hv_vcpu->stimer); i++)
> > - if (test_and_clear_bit(i, hv_vcpu->stimer_pending_bitmap)) {
> > - stimer = &hv_vcpu->stimer[i];
> > - if (stimer->config.enable) {
> > - exp_time = stimer->exp_time;
> > -
> > - if (exp_time) {
> > - time_now =
> > - get_time_ref_counter(vcpu->kvm);
> > - if (time_now >= exp_time)
> > - stimer_expiration(stimer);
> > - }
> > -
> > - if ((stimer->config.enable) &&
> > - stimer->count) {
> > - if (!stimer->msg_pending)
> > - stimer_start(stimer);
> > - } else
> > - stimer_cleanup(stimer);
> > - }
> > + for_each_test_and_clear_bit(i, hv_vcpu->stimer_pending_bitmap,
> > + ARRAY_SIZE(hv_vcpu->stimer)) {
> > + stimer = &hv_vcpu->stimer[i];
> > + if (!stimer->config.enable)
> > + continue;
> > +
> > + exp_time = stimer->exp_time;
> > +
> > + if (exp_time) {
> > + time_now = get_time_ref_counter(vcpu->kvm);
> > + if (time_now >= exp_time)
> > + stimer_expiration(stimer);
> > }
> > +
> > + if (stimer->count) {
>
> You can't drop 'stimer->config.enable' check here as stimer_expiration()
> call above actually changes it. This is done on purpose: oneshot timers
> fire only once so 'config.enable' is reset to 0.
Ok, I see. Will fix in v2
