* [PATCH RT 1/2] KVM: lapic: mark LAPIC timer handler as irqsafe
2015-05-14 14:07 [PATCH RT 0/2] Linux 3.4.107-rt134-rc1 Steven Rostedt
@ 2015-05-14 14:07 ` Steven Rostedt
2015-05-14 14:07 ` [PATCH RT 2/2] Linux 3.4.107-rt134-rc1 Steven Rostedt
1 sibling, 0 replies; 3+ messages in thread
From: Steven Rostedt @ 2015-05-14 14:07 UTC (permalink / raw)
To: linux-kernel, linux-rt-users
Cc: Thomas Gleixner, Carsten Emde, Sebastian Andrzej Siewior,
John Kacur, Paul Gortmaker, stable-rt, Marcelo Tosatti
[-- Attachment #1: 0001-KVM-lapic-mark-LAPIC-timer-handler-as-irqsafe.patch --]
[-- Type: text/plain, Size: 3333 bytes --]
3.4.107-rt134-rc1 stable review patch.
If anyone has any objections, please let me know.
------------------
From: Marcelo Tosatti <mtosatti@redhat.com>
Since lapic timer handler only wakes up a simple waitqueue,
it can be executed from hardirq context.
Also handle the case where hrtimer_start_expires fails due to -ETIME,
by injecting the interrupt to the guest immediately.
Reduces average cyclictest latency by 3us.
Cc: stable-rt@vger.kernel.org
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
arch/x86/kvm/lapic.c | 42 +++++++++++++++++++++++++++++++++++++++---
1 file changed, 39 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 578613da251e..b4bdc60f171f 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -683,8 +683,38 @@ static void update_divide_count(struct kvm_lapic *apic)
apic->divide_count);
}
+
+static enum hrtimer_restart apic_timer_fn(struct hrtimer *data);
+
+static void apic_timer_expired(struct hrtimer *data)
+{
+ int ret, i = 0;
+ enum hrtimer_restart r;
+ struct kvm_timer *ktimer = container_of(data, struct kvm_timer, timer);
+
+ r = apic_timer_fn(data);
+
+ if (r == HRTIMER_RESTART) {
+ do {
+ ret = hrtimer_start_expires(data, HRTIMER_MODE_ABS);
+ if (ret == -ETIME)
+ hrtimer_add_expires_ns(&ktimer->timer,
+ ktimer->period);
+ i++;
+ } while (ret == -ETIME && i < 10);
+
+ if (ret == -ETIME) {
+ printk_once(KERN_ERR "%s: failed to reprogram timer\n",
+ __func__);
+ WARN_ON_ONCE(1);
+ }
+ }
+}
+
+
static void start_apic_timer(struct kvm_lapic *apic)
{
+ int ret;
ktime_t now;
atomic_set(&apic->lapic_timer.pending, 0);
@@ -714,9 +744,11 @@ static void start_apic_timer(struct kvm_lapic *apic)
}
}
- hrtimer_start(&apic->lapic_timer.timer,
+ ret = hrtimer_start(&apic->lapic_timer.timer,
ktime_add_ns(now, apic->lapic_timer.period),
HRTIMER_MODE_ABS);
+ if (ret == -ETIME)
+ apic_timer_expired(&apic->lapic_timer.timer);
apic_debug("%s: bus cycle is %" PRId64 "ns, now 0x%016"
PRIx64 ", "
@@ -746,8 +778,10 @@ static void start_apic_timer(struct kvm_lapic *apic)
ns = (tscdeadline - guest_tsc) * 1000000ULL;
do_div(ns, this_tsc_khz);
}
- hrtimer_start(&apic->lapic_timer.timer,
+ ret = hrtimer_start(&apic->lapic_timer.timer,
ktime_add_ns(now, ns), HRTIMER_MODE_ABS);
+ if (ret == -ETIME)
+ apic_timer_expired(&apic->lapic_timer.timer);
local_irq_restore(flags);
}
@@ -1177,6 +1211,7 @@ int kvm_create_lapic(struct kvm_vcpu *vcpu)
hrtimer_init(&apic->lapic_timer.timer, CLOCK_MONOTONIC,
HRTIMER_MODE_ABS);
apic->lapic_timer.timer.function = kvm_timer_fn;
+ apic->lapic_timer.timer.irqsafe = 1;
apic->lapic_timer.t_ops = &lapic_timer_ops;
apic->lapic_timer.kvm = vcpu->kvm;
apic->lapic_timer.vcpu = vcpu;
@@ -1273,7 +1308,8 @@ void __kvm_migrate_apic_timer(struct kvm_vcpu *vcpu)
timer = &apic->lapic_timer.timer;
if (hrtimer_cancel(timer))
- hrtimer_start_expires(timer, HRTIMER_MODE_ABS);
+ if (hrtimer_start_expires(timer, HRTIMER_MODE_ABS) == -ETIME)
+ apic_timer_expired(timer);
}
void kvm_lapic_sync_from_vapic(struct kvm_vcpu *vcpu)
--
2.1.4
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