Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753252AbXJULLg (ORCPT ); Sun, 21 Oct 2007 07:11:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752036AbXJULIB (ORCPT ); Sun, 21 Oct 2007 07:08:01 -0400 Received: from il.qumranet.com ([82.166.9.18]:58449 "EHLO il.qumranet.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751513AbXJULH4 (ORCPT ); Sun, 21 Oct 2007 07:07:56 -0400 From: Avi Kivity To: kvm-devel@lists.sourceforge.net Cc: linux-kernel@vger.kernel.org, Kevin Pedretti , Avi Kivity Subject: [PATCH 11/11] KVM: Improve local apic timer wraparound handling Date: Sun, 21 Oct 2007 13:08:12 +0200 Message-Id: <11929648924174-git-send-email-avi@qumranet.com> X-Mailer: git-send-email 1.5.3 In-Reply-To: <1192964892617-git-send-email-avi@qumranet.com> References: <1192964892617-git-send-email-avi@qumranet.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2405 Lines: 80 From: Kevin Pedretti Better handle wrap-around cases when reading the APIC CCR (current count register). Also, if ICR is 0, CCR should also be 0... previously reading CCR before setting ICR would result in a large kinda-random number. Signed-off-by: Kevin Pedretti Signed-off-by: Avi Kivity --- drivers/kvm/lapic.c | 36 ++++++++++++++++++++++++++---------- 1 files changed, 26 insertions(+), 10 deletions(-) diff --git a/drivers/kvm/lapic.c b/drivers/kvm/lapic.c index 443730e..238fcad 100644 --- a/drivers/kvm/lapic.c +++ b/drivers/kvm/lapic.c @@ -494,12 +494,19 @@ static void apic_send_ipi(struct kvm_lapic *apic) static u32 apic_get_tmcct(struct kvm_lapic *apic) { - u32 counter_passed; - ktime_t passed, now = apic->timer.dev.base->get_time(); - u32 tmcct = apic_get_reg(apic, APIC_TMICT); + u64 counter_passed; + ktime_t passed, now; + u32 tmcct; ASSERT(apic != NULL); + now = apic->timer.dev.base->get_time(); + tmcct = apic_get_reg(apic, APIC_TMICT); + + /* if initial count is 0, current count should also be 0 */ + if (tmcct == 0) + return 0; + if (unlikely(ktime_to_ns(now) <= ktime_to_ns(apic->timer.last_update))) { /* Wrap around */ @@ -514,15 +521,24 @@ static u32 apic_get_tmcct(struct kvm_lapic *apic) counter_passed = div64_64(ktime_to_ns(passed), (APIC_BUS_CYCLE_NS * apic->timer.divide_count)); - tmcct -= counter_passed; - if (tmcct <= 0) { - if (unlikely(!apic_lvtt_period(apic))) + if (counter_passed > tmcct) { + if (unlikely(!apic_lvtt_period(apic))) { + /* one-shot timers stick at 0 until reset */ tmcct = 0; - else - do { - tmcct += apic_get_reg(apic, APIC_TMICT); - } while (tmcct <= 0); + } else { + /* + * periodic timers reset to APIC_TMICT when they + * hit 0. The while loop simulates this happening N + * times. (counter_passed %= tmcct) would also work, + * but might be slower or not work on 32-bit?? + */ + while (counter_passed > tmcct) + counter_passed -= tmcct; + tmcct -= counter_passed; + } + } else { + tmcct -= counter_passed; } return tmcct; -- 1.5.3 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/