KVM: LAPIC: Mark hrtimer to expire in hard interrupt context (2c0d278f) · Commits · 戴 / test

On PREEMPT_RT enabled kernels unmarked hrtimers are moved into soft interrupt expiry mode by default. While that's not a functional requirement for the KVM local APIC timer emulation, it's a latency issue which can be avoided by marking the timer so hard interrupt context expiry is enforced. No functional change. [ tglx: Split out from larger combo patch. Add changelog. ] Signed-off-by:

Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by:

Thomas Gleixner <tglx@linutronix.de> Acked-by:

Paolo Bonzini <pbonzini@redhat.com> Acked-by:

Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20190726185753.363363474@linutronix.de

arch/x86/kvm/lapic.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -1601,7 +1601,7 @@ static void start_sw_tscdeadline(struct kvm_lapic *apic)
		likely(ns > apic->lapic_timer.timer_advance_ns)) {
		expire = ktime_add_ns(now, ns);
		expire = ktime_sub_ns(expire, ktimer->timer_advance_ns);
		hrtimer_start(&ktimer->timer, expire, HRTIMER_MODE_ABS);
		hrtimer_start(&ktimer->timer, expire, HRTIMER_MODE_ABS_HARD);
		} else
		apic_timer_expired(apic);

		@@ -2302,7 +2302,7 @@ int kvm_create_lapic(struct kvm_vcpu *vcpu, int timer_advance_ns)
		apic->vcpu = vcpu;

		hrtimer_init(&apic->lapic_timer.timer, CLOCK_MONOTONIC,
		HRTIMER_MODE_ABS);
		HRTIMER_MODE_ABS_HARD);
		apic->lapic_timer.timer.function = apic_timer_fn;
		if (timer_advance_ns == -1) {
		apic->lapic_timer.timer_advance_ns = LAPIC_TIMER_ADVANCE_ADJUST_INIT;
		@@ -2487,7 +2487,7 @@ void __kvm_migrate_apic_timer(struct kvm_vcpu *vcpu)

		timer = &vcpu->arch.apic->lapic_timer.timer;
		if (hrtimer_cancel(timer))
		hrtimer_start_expires(timer, HRTIMER_MODE_ABS);
		hrtimer_start_expires(timer, HRTIMER_MODE_ABS_HARD);
		}

		/*

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