102 lines
3.1 KiB
Diff
102 lines
3.1 KiB
Diff
From: Marcelo Tosatti <mtosatti@redhat.com>
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Date: Wed, 8 Apr 2015 20:33:25 -0300
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Subject: KVM: lapic: mark LAPIC timer handler as irqsafe
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.1/patches-4.1.3-rt3.tar.xz
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Since lapic timer handler only wakes up a simple waitqueue,
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it can be executed from hardirq context.
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Also handle the case where hrtimer_start_expires fails due to -ETIME,
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by injecting the interrupt to the guest immediately.
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Reduces average cyclictest latency by 3us.
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Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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arch/x86/kvm/lapic.c | 40 +++++++++++++++++++++++++++++++++++++---
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1 file changed, 37 insertions(+), 3 deletions(-)
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--- a/arch/x86/kvm/lapic.c
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+++ b/arch/x86/kvm/lapic.c
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@@ -1167,8 +1167,36 @@ void wait_lapic_expire(struct kvm_vcpu *
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__delay(tsc_deadline - guest_tsc);
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}
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+static enum hrtimer_restart apic_timer_fn(struct hrtimer *data);
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+
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+static void __apic_timer_expired(struct hrtimer *data)
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+{
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+ int ret, i = 0;
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+ enum hrtimer_restart r;
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+ struct kvm_timer *ktimer = container_of(data, struct kvm_timer, timer);
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+
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+ r = apic_timer_fn(data);
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+
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+ if (r == HRTIMER_RESTART) {
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+ do {
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+ ret = hrtimer_start_expires(data, HRTIMER_MODE_ABS);
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+ if (ret == -ETIME)
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+ hrtimer_add_expires_ns(&ktimer->timer,
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+ ktimer->period);
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+ i++;
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+ } while (ret == -ETIME && i < 10);
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+
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+ if (ret == -ETIME) {
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+ printk_once(KERN_ERR "%s: failed to reprogram timer\n",
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+ __func__);
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+ WARN_ON_ONCE(1);
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+ }
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+ }
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+}
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+
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static void start_apic_timer(struct kvm_lapic *apic)
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{
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+ int ret;
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ktime_t now;
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atomic_set(&apic->lapic_timer.pending, 0);
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@@ -1199,9 +1227,11 @@ static void start_apic_timer(struct kvm_
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}
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}
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- hrtimer_start(&apic->lapic_timer.timer,
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+ ret = hrtimer_start(&apic->lapic_timer.timer,
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ktime_add_ns(now, apic->lapic_timer.period),
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HRTIMER_MODE_ABS);
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+ if (ret == -ETIME)
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+ __apic_timer_expired(&apic->lapic_timer.timer);
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apic_debug("%s: bus cycle is %" PRId64 "ns, now 0x%016"
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PRIx64 ", "
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@@ -1233,8 +1263,10 @@ static void start_apic_timer(struct kvm_
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do_div(ns, this_tsc_khz);
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expire = ktime_add_ns(now, ns);
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expire = ktime_sub_ns(expire, lapic_timer_advance_ns);
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- hrtimer_start(&apic->lapic_timer.timer,
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+ ret = hrtimer_start(&apic->lapic_timer.timer,
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expire, HRTIMER_MODE_ABS);
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+ if (ret == -ETIME)
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+ __apic_timer_expired(&apic->lapic_timer.timer);
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} else
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apic_timer_expired(apic);
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@@ -1707,6 +1739,7 @@ int kvm_create_lapic(struct kvm_vcpu *vc
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hrtimer_init(&apic->lapic_timer.timer, CLOCK_MONOTONIC,
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HRTIMER_MODE_ABS);
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apic->lapic_timer.timer.function = apic_timer_fn;
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+ apic->lapic_timer.timer.irqsafe = 1;
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/*
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* APIC is created enabled. This will prevent kvm_lapic_set_base from
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@@ -1834,7 +1867,8 @@ void __kvm_migrate_apic_timer(struct kvm
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timer = &vcpu->arch.apic->lapic_timer.timer;
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if (hrtimer_cancel(timer))
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- hrtimer_start_expires(timer, HRTIMER_MODE_ABS);
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+ if (hrtimer_start_expires(timer, HRTIMER_MODE_ABS) == -ETIME)
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+ __apic_timer_expired(timer);
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}
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/*
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