From mboxrd@z Thu Jan 1 00:00:00 1970 From: 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> References: <1192964892617-git-send-email-avi@qumranet.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Kevin Pedretti , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Avi Kivity To: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Return-path: In-Reply-To: <1192964892617-git-send-email-avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org 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 ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/