From 1e0ad70cc1957b9050368e433b1061a2cd1ce543 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= Date: Fri, 10 Oct 2014 19:15:09 +0200 Subject: [PATCH] KVM: x86: fix deadline tsc interrupt injection MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit The check in kvm_set_lapic_tscdeadline_msr() was trying to prevent a situation where we lose a pending deadline timer in a MSR write. Losing it is fine, because it effectively occurs before the timer fired, so we should be able to cancel or postpone it. Another problem comes from interaction with QEMU, or other userspace that can set deadline MSR without a good reason, when timer is already pending: one guest's deadline request results in more than one interrupt because one is injected immediately on MSR write from userspace and one through hrtimer later. The solution is to remove the injection when replacing a pending timer and to improve the usual QEMU path, we inject without a hrtimer when the deadline has already passed. Signed-off-by: Radim Krčmář Reported-by: Nadav Amit Signed-off-by: Paolo Bonzini --- arch/x86/kvm/lapic.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 1ebd7ff33ac7..66dd1731ab99 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -1132,9 +1132,10 @@ static void start_apic_timer(struct kvm_lapic *apic) if (likely(tscdeadline > guest_tsc)) { ns = (tscdeadline - guest_tsc) * 1000000ULL; do_div(ns, this_tsc_khz); - } - hrtimer_start(&apic->lapic_timer.timer, - ktime_add_ns(now, ns), HRTIMER_MODE_ABS); + hrtimer_start(&apic->lapic_timer.timer, + ktime_add_ns(now, ns), HRTIMER_MODE_ABS); + } else + apic_timer_expired(apic); local_irq_restore(flags); } @@ -1391,9 +1392,6 @@ void kvm_set_lapic_tscdeadline_msr(struct kvm_vcpu *vcpu, u64 data) return; hrtimer_cancel(&apic->lapic_timer.timer); - /* Inject here so clearing tscdeadline won't override new value */ - if (apic_has_pending_timer(vcpu)) - kvm_inject_apic_timer_irqs(vcpu); apic->lapic_timer.tscdeadline = data; start_apic_timer(apic); } -- 2.20.1