From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965162AbbENOHn (ORCPT ); Thu, 14 May 2015 10:07:43 -0400 Received: from mail.kernel.org ([198.145.29.136]:36334 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933473AbbENOHd (ORCPT ); Thu, 14 May 2015 10:07:33 -0400 Message-Id: <20150514140729.254698453@goodmis.org> User-Agent: quilt/0.61-1 Date: Thu, 14 May 2015 10:07:22 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org, linux-rt-users Cc: Thomas Gleixner , Carsten Emde , Sebastian Andrzej Siewior , John Kacur , Paul Gortmaker , , Marcelo Tosatti Subject: [PATCH RT 1/2] KVM: lapic: mark LAPIC timer handler as irqsafe References: <20150514140721.234319563@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Disposition: inline; filename=0001-KVM-lapic-mark-LAPIC-timer-handler-as-irqsafe.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.4.107-rt134-rc1 stable review patch. If anyone has any objections, please let me know. ------------------ From: Marcelo Tosatti 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 Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Steven Rostedt --- 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