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authorAnthoine Bourgeois <anthoine.bourgeois@blade-group.com>2018-04-29 22:05:58 +0000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-05-16 10:10:32 +0200
commite8bbbd11e6376e102075378b97d2f0313129fbe3 (patch)
tree1b27fd19cc1c994434daef6bfecfe4f9bc06167e
parent5138dd0db530548f3390098636e3e36cd7681eec (diff)
KVM: x86: remove APIC Timer periodic/oneshot spikes
commit ecf08dad723d3e000aecff6c396f54772d124733 upstream. Since the commit "8003c9ae204e: add APIC Timer periodic/oneshot mode VMX preemption timer support", a Windows 10 guest has some erratic timer spikes. Here the results on a 150000 times 1ms timer without any load: Before 8003c9ae204e | After 8003c9ae204e Max 1834us | 86000us Mean 1100us | 1021us Deviation 59us | 149us Here the results on a 150000 times 1ms timer with a cpu-z stress test: Before 8003c9ae204e | After 8003c9ae204e Max 32000us | 140000us Mean 1006us | 1997us Deviation 140us | 11095us The root cause of the problem is starting hrtimer with an expiry time already in the past can take more than 20 milliseconds to trigger the timer function. It can be solved by forward such past timers immediately, rather than submitting them to hrtimer_start(). In case the timer is periodic, update the target expiration and call hrtimer_start with it. v2: Check if the tsc deadline is already expired. Thank you Mika. v3: Execute the past timers immediately rather than submitting them to hrtimer_start(). v4: Rearm the periodic timer with advance_periodic_target_expiration() a simpler version of set_target_expiration(). Thank you Paolo. Cc: Mika Penttilä <mika.penttila@nextfour.com> Cc: Wanpeng Li <kernellwp@gmail.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Anthoine Bourgeois <anthoine.bourgeois@blade-group.com> 8003c9ae204e ("KVM: LAPIC: add APIC Timer periodic/oneshot mode VMX preemption timer support") Signed-off-by: Radim Krčmář <rkrcmar@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/x86/kvm/lapic.c37
1 files changed, 20 insertions, 17 deletions
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 8cfdb6484fd0..ab8993fe58cc 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1418,23 +1418,6 @@ static void start_sw_tscdeadline(struct kvm_lapic *apic)
local_irq_restore(flags);
}
-static void start_sw_period(struct kvm_lapic *apic)
-{
- if (!apic->lapic_timer.period)
- return;
-
- if (apic_lvtt_oneshot(apic) &&
- ktime_after(ktime_get(),
- apic->lapic_timer.target_expiration)) {
- apic_timer_expired(apic);
- return;
- }
-
- hrtimer_start(&apic->lapic_timer.timer,
- apic->lapic_timer.target_expiration,
- HRTIMER_MODE_ABS_PINNED);
-}
-
static bool set_target_expiration(struct kvm_lapic *apic)
{
ktime_t now;
@@ -1491,6 +1474,26 @@ static void advance_periodic_target_expiration(struct kvm_lapic *apic)
apic->lapic_timer.period);
}
+static void start_sw_period(struct kvm_lapic *apic)
+{
+ if (!apic->lapic_timer.period)
+ return;
+
+ if (ktime_after(ktime_get(),
+ apic->lapic_timer.target_expiration)) {
+ apic_timer_expired(apic);
+
+ if (apic_lvtt_oneshot(apic))
+ return;
+
+ advance_periodic_target_expiration(apic);
+ }
+
+ hrtimer_start(&apic->lapic_timer.timer,
+ apic->lapic_timer.target_expiration,
+ HRTIMER_MODE_ABS_PINNED);
+}
+
bool kvm_lapic_hv_timer_in_use(struct kvm_vcpu *vcpu)
{
if (!lapic_in_kernel(vcpu))