[Qemu-devel] [7231] Change RTC time drift IRQ re-injection (Gleb Natapov)

[Anthony Liguori]

Revision: 7231
          http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=7231
Author:   aliguori
Date:     2009-04-22 20:20:22 +0000 (Wed, 22 Apr 2009)
Log Message:
-----------
Change RTC time drift IRQ re-injection (Gleb Natapov)

Currently IRQ are reinjected as soon as they are acknowledged to
the RTC, but Windows sometimes do acknowledgement in a loop with
global interrupt disabled waiting for interrupt to be cleared and
it does not mask RTC vector in PIC/APIC while doing this. In such
situation interrupt injection always fails and RTC interrupt is never
cleared.

Instead of reinjecting coalesced IRQs on acknowledgement the patch below
reinjects them by accelerating RTC clock a bit. This way RTC interrupt
is not constantly raced after coalesced interrupt.

Signed-off-by: Gleb Natapov <address@hidden>
Signed-off-by: Anthony Liguori <address@hidden>

Modified Paths:
--------------
    trunk/hw/mc146818rtc.c

Modified: trunk/hw/mc146818rtc.c
===================================================================
--- trunk/hw/mc146818rtc.c      2009-04-22 20:20:07 UTC (rev 7230)
+++ trunk/hw/mc146818rtc.c      2009-04-22 20:20:22 UTC (rev 7231)
@@ -73,6 +73,7 @@
 #ifdef TARGET_I386
     uint32_t irq_coalesced;
     uint32_t period;
+    QEMUTimer *coalesced_timer;
 #endif
     QEMUTimer *second_timer;
     QEMUTimer *second_timer2;
@@ -93,6 +94,37 @@
 static void rtc_set_time(RTCState *s);
 static void rtc_copy_date(RTCState *s);
 
+#ifdef TARGET_I386
+static void rtc_coalesced_timer_update(RTCState *s)
+{
+    if (s->irq_coalesced == 0) {
+        qemu_del_timer(s->coalesced_timer);
+    } else {
+        /* divide each RTC interval to 2 - 8 smaller intervals */
+        int c = MIN(s->irq_coalesced, 7) + 1; 
+        int64_t next_clock = qemu_get_clock(vm_clock) +
+               muldiv64(s->period / c, ticks_per_sec, 32768);
+        qemu_mod_timer(s->coalesced_timer, next_clock);
+    }
+}
+
+static void rtc_coalesced_timer(void *opaque)
+{
+    RTCState *s = opaque;
+
+    if (s->irq_coalesced != 0) {
+        apic_reset_irq_delivered();
+        s->cmos_data[RTC_REG_C] |= 0xc0;
+        rtc_irq_raise(s->irq);
+        if (apic_get_irq_delivered()) {
+            s->irq_coalesced--;
+        }
+    }
+
+    rtc_coalesced_timer_update(s);
+}
+#endif
+
 static void rtc_timer_update(RTCState *s, int64_t current_time)
 {
     int period_code, period;
@@ -138,14 +170,18 @@
     RTCState *s = opaque;
 
     rtc_timer_update(s, s->next_periodic_time);
+    if (s->cmos_data[RTC_REG_B] & REG_B_PIE) {
+        s->cmos_data[RTC_REG_C] |= 0xc0;
 #ifdef TARGET_I386
-    if ((s->cmos_data[RTC_REG_C] & 0xc0) && rtc_td_hack) {
-        s->irq_coalesced++;
-        return;
-    }
+        if(rtc_td_hack) {
+            apic_reset_irq_delivered();
+            rtc_irq_raise(s->irq);
+            if (!apic_get_irq_delivered()) {
+                s->irq_coalesced++;
+                rtc_coalesced_timer_update(s);
+            }
+        } else
 #endif
-    if (s->cmos_data[RTC_REG_B] & REG_B_PIE) {
-        s->cmos_data[RTC_REG_C] |= 0xc0;
         rtc_irq_raise(s->irq);
     }
     if (s->cmos_data[RTC_REG_B] & REG_B_SQWE) {
@@ -415,15 +451,6 @@
         case RTC_REG_C:
             ret = s->cmos_data[s->cmos_index];
             qemu_irq_lower(s->irq);
-#ifdef TARGET_I386
-            if(s->irq_coalesced) {
-                apic_reset_irq_delivered();
-                qemu_irq_raise(s->irq);
-                if (apic_get_irq_delivered())
-                    s->irq_coalesced--;
-                break;
-            }
-#endif
             s->cmos_data[RTC_REG_C] = 0x00;
             break;
         default:
@@ -536,6 +563,7 @@
 
     s->irq_coalesced = qemu_get_be32(f);
     s->period = qemu_get_be32(f);
+    rtc_coalesced_timer_update(s);
     return 0;
 }
 #endif
@@ -558,6 +586,10 @@
 
     s->periodic_timer = qemu_new_timer(vm_clock,
                                        rtc_periodic_timer, s);
+#ifdef TARGET_I386
+    if (rtc_td_hack)
+        s->coalesced_timer = qemu_new_timer(vm_clock, rtc_coalesced_timer, s);
+#endif
     s->second_timer = qemu_new_timer(vm_clock,
                                      rtc_update_second, s);
     s->second_timer2 = qemu_new_timer(vm_clock,