From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753664AbbANRQK (ORCPT ); Wed, 14 Jan 2015 12:16:10 -0500 Received: from mx1.redhat.com ([209.132.183.28]:53973 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752409AbbANRQG (ORCPT ); Wed, 14 Jan 2015 12:16:06 -0500 Message-Id: <20150114171459.694888126@redhat.com> User-Agent: quilt/0.60-1 Date: Wed, 14 Jan 2015 15:12:53 -0200 From: Marcelo Tosatti To: linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org Cc: Luiz Capitulino , Rik van Riel , Steven Rostedt , Thomas Gleixner , kvm@vger.kernel.org, Paolo Bonzini , Marcelo Tosatti Subject: [patch -rt 2/2] KVM: lapic: mark LAPIC timer handler as irqsafe References: <20150114171251.882318257@redhat.com> Content-Disposition: inline; filename=kvm-lapic-irqsafe Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Since lapic timer handler only wakes up a simple waitqueue, it can be executed from hardirq context. Reduces average cyclictest latency by 3us. Signed-off-by: Marcelo Tosatti --- arch/x86/kvm/lapic.c | 42 +++++++++++++++++++++++++++++++++++++++--- 1 file changed, 39 insertions(+), 3 deletions(-) Index: linux-stable-rt/arch/x86/kvm/lapic.c =================================================================== --- linux-stable-rt.orig/arch/x86/kvm/lapic.c 2014-11-25 14:14:38.636810068 -0200 +++ linux-stable-rt/arch/x86/kvm/lapic.c 2015-01-14 14:59:17.840251874 -0200 @@ -1031,8 +1031,38 @@ 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); @@ -1062,9 +1092,11 @@ } } - 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 ", " @@ -1094,8 +1126,10 @@ 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); } @@ -1581,6 +1615,7 @@ hrtimer_init(&apic->lapic_timer.timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); apic->lapic_timer.timer.function = apic_timer_fn; + apic->lapic_timer.timer.irqsafe = 1; /* * APIC is created enabled. This will prevent kvm_lapic_set_base from @@ -1699,7 +1734,8 @@ timer = &vcpu->arch.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); } /*