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    SubjectRe: [PATCH 13/34] KVM: x86: hyper-v: optimize and cleanup kvm_hv_process_stimers()
    On Mon, Nov 20, 2023 at 03:26:08PM +0100, Vitaly Kuznetsov wrote:
    > Yury Norov <yury.norov@gmail.com> 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@gmail.com>
    > > ---
    > > 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

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