| Date | Thu, 1 Aug 2019 08:55:58 -0700 | From | tip-bot for Sebastian Andrzej Siewior <> | Subject | [tip:timers/core] KVM: LAPIC: Mark hrtimer to expire in hard interrupt context |
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Commit-ID: 4ca8f0af37956ca39f65c8c4d500e4fb93590433 Gitweb: https://git.kernel.org/tip/4ca8f0af37956ca39f65c8c4d500e4fb93590433 Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de> AuthorDate: Fri, 26 Jul 2019 20:30:55 +0200 Committer: Thomas Gleixner <tglx@linutronix.de> CommitDate: Thu, 1 Aug 2019 17:43:18 +0200
KVM: LAPIC: Mark hrtimer to expire in hard interrupt context
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 | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 0aa158657f20..b9e516099d07 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -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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