From ae11a1ea30f43abebd96a22988619eb9f52e6a4e Mon Sep 17 00:00:00 2001

From: Marcelo Tosatti <mtosatti@redhat.com>

Date: Wed, 4 Dec 2019 15:21:07 +0100

Subject: [PATCH 1/3] mc146818rtc: fix timer interrupt reinjection

RH-Author: Marcelo Tosatti <mtosatti@redhat.com>

Message-id: <20191204152436.680299856@amt.cnet>

Patchwork-id: 92889

O-Subject: [RHEL-7.8 qemu-kvm-rhev PATCH 1/3] mc146818rtc: fix timer interrupt reinjection

Bugzilla: 1639098

RH-Acked-by: Laszlo Ersek <lersek@redhat.com>

RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>

RH-Acked-by: Vitaly Kuznetsov <vkuznets@redhat.com>

BZ: 1639098

Brew: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=24854309

BRANCH: rhv7/master-2.12.0

Upstream: b429de730174b388ea5760e3debb0d542ea3c261

of pbonzini's for-upstream tree.

commit 369b41359af46bded5799c9ef8be2b641d92e043 broke timer interrupt

reinjection when there is no period change by the guest.

In that case, old_period is 0, which ends up zeroing irq_coalesced

(counter of reinjected interrupts).

The consequence is Windows 7 is unable to synchronize time via NTP.

Easily reproducible by playing a fullscreen video with cirrus and VNC.

Fix by not updating s->irq_coalesced when old_period is 0.

V2: reorganize code (Paolo Bonzini)

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Message-Id: <20191010123008.GA19158@amt.cnet>

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

---

 hw/timer/mc146818rtc.c | 53 +++++++++++++++++++++++++-------------------------

 1 file changed, 27 insertions(+), 26 deletions(-)

diff --git a/hw/timer/mc146818rtc.c b/hw/timer/mc146818rtc.c

index 68c353f..296d974 100644

--- a/hw/timer/mc146818rtc.c

+++ b/hw/timer/mc146818rtc.c

@@ -197,24 +197,28 @@ periodic_timer_update(RTCState *s, int64_t current_time, uint32_t old_period)

     period = rtc_periodic_clock_ticks(s);

-    if (period) {

-        /* compute 32 khz clock */

-        cur_clock =

-            muldiv64(current_time, RTC_CLOCK_RATE, NANOSECONDS_PER_SECOND);

+    if (!period) {

+        s->irq_coalesced = 0;

+        timer_del(s->periodic_timer);

+        return;

+    }

-        /*

-        * if the periodic timer's update is due to period re-configuration,

-        * we should count the clock since last interrupt.

-        */

-        if (old_period) {

-            int64_t last_periodic_clock, next_periodic_clock;

-

-            next_periodic_clock = muldiv64(s->next_periodic_time,

-                                    RTC_CLOCK_RATE, NANOSECONDS_PER_SECOND);

-            last_periodic_clock = next_periodic_clock - old_period;

-            lost_clock = cur_clock - last_periodic_clock;

-            assert(lost_clock >= 0);

-        }

+    /* compute 32 khz clock */

+    cur_clock =

+        muldiv64(current_time, RTC_CLOCK_RATE, NANOSECONDS_PER_SECOND);

+

+    /*

+     * if the periodic timer's update is due to period re-configuration,

+     * we should count the clock since last interrupt.

+     */

+    if (old_period) {

+        int64_t last_periodic_clock, next_periodic_clock;

+

+        next_periodic_clock = muldiv64(s->next_periodic_time,

+                                RTC_CLOCK_RATE, NANOSECONDS_PER_SECOND);

+        last_periodic_clock = next_periodic_clock - old_period;

+        lost_clock = cur_clock - last_periodic_clock;

+        assert(lost_clock >= 0);

         /*

          * s->irq_coalesced can change for two reasons:

@@ -245,22 +249,19 @@ periodic_timer_update(RTCState *s, int64_t current_time, uint32_t old_period)

                 rtc_coalesced_timer_update(s);

             }

         } else {

-           /*

+            /*

              * no way to compensate the interrupt if LOST_TICK_POLICY_SLEW

              * is not used, we should make the time progress anyway.

              */

             lost_clock = MIN(lost_clock, period);

         }

+    }

-        assert(lost_clock >= 0 && lost_clock <= period);

+    assert(lost_clock >= 0 && lost_clock <= period);

-        next_irq_clock = cur_clock + period - lost_clock;

-        s->next_periodic_time = periodic_clock_to_ns(next_irq_clock) + 1;

-        timer_mod(s->periodic_timer, s->next_periodic_time);

-    } else {

-        s->irq_coalesced = 0;

-        timer_del(s->periodic_timer);

-    }

+    next_irq_clock = cur_clock + period - lost_clock;

+    s->next_periodic_time = periodic_clock_to_ns(next_irq_clock) + 1;

+    timer_mod(s->periodic_timer, s->next_periodic_time);

 }

 static void rtc_periodic_timer(void *opaque)

-- 

1.8.3.1