From f1ba5cfbe47a90f801598a908fd2157bbab2ce1a Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 16 Apr 2019 13:32:45 -0700 Subject: [PATCH] KVM: lapic: Explicitly cancel the hv timer if it's pre-expired Explicitly call cancel_hv_timer() instead of returning %false to coerce restart_apic_timer() into canceling it by way of start_sw_timer(). Functionally, the existing code is correct in the sense that it doesn't doing anything visibily wrong, e.g. generate spurious interrupts or miss an interrupt. But it's extremely confusing and inefficient, e.g. there are multiple extraneous calls to apic_timer_expired() that effectively get dropped due to @timer_pending being %true. Cc: Wanpeng Li Cc: Liran Alon Signed-off-by: Sean Christopherson Signed-off-by: Paolo Bonzini --- arch/x86/kvm/lapic.c | 22 +++++++++++++++------- 1 file changed, 15 insertions(+), 7 deletions(-) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 7eef076bc5ee..61d1cbab877e 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -1693,17 +1693,25 @@ static bool start_hv_timer(struct kvm_lapic *apic) hrtimer_cancel(&ktimer->timer); /* - * Also recheck ktimer->pending, in case the sw timer triggered in - * the window. For periodic timer, leave the hv timer running for - * simplicity, and the deadline will be recomputed on the next vmexit. + * To simplify handling the periodic timer, leave the hv timer running + * even if the deadline timer has expired, i.e. rely on the resulting + * VM-Exit to recompute the periodic timer's target expiration. */ - if (!apic_lvtt_period(apic) && (r || atomic_read(&ktimer->pending))) { - if (r) + if (!apic_lvtt_period(apic)) { + /* + * Cancel the hv timer if the sw timer fired while the hv timer + * was being programmed, or if the hv timer itself expired. + */ + if (atomic_read(&ktimer->pending)) { + cancel_hv_timer(apic); + } else if (r) { apic_timer_expired(apic); - return false; + cancel_hv_timer(apic); + } } - trace_kvm_hv_timer_state(apic->vcpu->vcpu_id, true); + trace_kvm_hv_timer_state(apic->vcpu->vcpu_id, ktimer->hv_timer_in_use); + return true; }