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SubjectRe: [patch 07/12] KVM: LAPIC: Mark hrtimer to expire in hard interrupt context
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On 26/07/19 20:30, Thomas Gleixner wrote:
> From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
>
> 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>
> Cc: kvm@vger.kernel.org
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> ---
> arch/x86/kvm/lapic.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -2302,7 +2302,7 @@ int kvm_create_lapic(struct kvm_vcpu *vc
> 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;
>
>

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

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