From 8af16b9722f5bdeacf3a30c21490846e24b989b2 Mon Sep 17 00:00:00 2001

From: Marcelo Tosatti <mtosatti@redhat.com>

Date: Wed, 4 Dec 2019 15:21:08 +0100

Subject: [PATCH 2/3] Revert "mc146818rtc: fix timer interrupt reinjection"

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

Message-id: <20191204152436.753293175@amt.cnet>

Patchwork-id: 92888

O-Subject: [RHEL-7.8 qemu-kvm-rhev PATCH 2/3] Revert "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: 3ae32adff17226bc6a5f3fd7bb9804e6779e0660

of pbonzini's for-upstream tree.

This reverts commit b429de730174b388ea5760e3debb0d542ea3c261, except

that the reversal of the outer "if (period)" is left in.

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

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

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

---

 hw/timer/mc146818rtc.c | 67 +++++++++++++++++++++++++-------------------------

 1 file changed, 33 insertions(+), 34 deletions(-)

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

index 296d974..d848911 100644

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

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

@@ -196,7 +196,6 @@ periodic_timer_update(RTCState *s, int64_t current_time, uint32_t old_period)

     int64_t cur_clock, next_irq_clock, lost_clock = 0;

     period = rtc_periodic_clock_ticks(s);

-

     if (!period) {

         s->irq_coalesced = 0;

         timer_del(s->periodic_timer);

@@ -219,42 +218,42 @@ periodic_timer_update(RTCState *s, int64_t current_time, uint32_t old_period)

         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:

+     *

+     * a) if one or more periodic timer interrupts have been lost,

+     *    lost_clock will be more that a period.

+     *

+     * b) when the period may be reconfigured, we expect the OS to

+     *    treat delayed tick as the new period.  So, when switching

+     *    from a shorter to a longer period, scale down the missing,

+     *    because the OS will treat past delayed ticks as longer

+     *    (leftovers are put back into lost_clock).  When switching

+     *    to a shorter period, scale up the missing ticks since the

+     *    OS handler will treat past delayed ticks as shorter.

+     */

+    if (s->lost_tick_policy == LOST_TICK_POLICY_SLEW) {

+        uint32_t old_irq_coalesced = s->irq_coalesced;

+

+        s->period = period;

+        lost_clock += old_irq_coalesced * old_period;

+        s->irq_coalesced = lost_clock / s->period;

+        lost_clock %= s->period;

+        if (old_irq_coalesced != s->irq_coalesced ||

+            old_period != s->period) {

+            DPRINTF_C("cmos: coalesced irqs scaled from %d to %d, "

+                      "period scaled from %d to %d\n", old_irq_coalesced,

+                      s->irq_coalesced, old_period, s->period);

+            rtc_coalesced_timer_update(s);

+        }

+    } else {

         /*

-         * s->irq_coalesced can change for two reasons:

-         *

-         * a) if one or more periodic timer interrupts have been lost,

-         *    lost_clock will be more that a period.

-         *

-         * b) when the period may be reconfigured, we expect the OS to

-         *    treat delayed tick as the new period.  So, when switching

-         *    from a shorter to a longer period, scale down the missing,

-         *    because the OS will treat past delayed ticks as longer

-         *    (leftovers are put back into lost_clock).  When switching

-         *    to a shorter period, scale up the missing ticks since the

-         *    OS handler will treat past delayed ticks as shorter.

+         * no way to compensate the interrupt if LOST_TICK_POLICY_SLEW

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

          */

-        if (s->lost_tick_policy == LOST_TICK_POLICY_SLEW) {

-            uint32_t old_irq_coalesced = s->irq_coalesced;

-

-            s->period = period;

-            lost_clock += old_irq_coalesced * old_period;

-            s->irq_coalesced = lost_clock / s->period;

-            lost_clock %= s->period;

-            if (old_irq_coalesced != s->irq_coalesced ||

-                old_period != s->period) {

-                DPRINTF_C("cmos: coalesced irqs scaled from %d to %d, "

-                          "period scaled from %d to %d\n", old_irq_coalesced,

-                          s->irq_coalesced, old_period, s->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);

-        }

+        lost_clock = MIN(lost_clock, period);

     }

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

-- 

1.8.3.1