fix rtc-td-hack on host without high-res timers

On hosts without high-res timers it is impossible to inject rtc interrupt
faster then 1kHz. Windows sometimes configures RTC to generate 1kHz
interrupts, so we can't inject missed interrupts when running on such
hosts. Always injecting an interrupt on REG_C read is also not an option
since Windows wait for REG_C to become zero with interrupt disabled
during boot. This patch uses mixed approach: accelerate timer + inject
up to 1000 interrupts on REG_C read.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
(cherry picked from commit ba32edab7fdab0e74b54696942b4127d26861cf6)

diff --git a/hw/mc146818rtc.c b/hw/mc146818rtc.c
index b8c7b0c1b8b0f218702d4bba3a619ecac6a67e47..e4d55c7c79f67567134dae627b87cd42a5b6454d 100644 (file)
--- a/hw/mc146818rtc.c
+++ b/hw/mc146818rtc.c
@@ -30,6 +30,8 @@
 
 //#define DEBUG_CMOS
 
+#define RTC_REINJECT_ON_ACK_COUNT 1000
+
 #define RTC_SECONDS             0
 #define RTC_SECONDS_ALARM       1
 #define RTC_MINUTES             2
@@ -76,6 +78,7 @@ struct RTCState {
     int64_t next_periodic_time;
     /* second update */
     int64_t next_second_time;
+    uint16_t irq_reinject_on_ack_count;
     uint32_t irq_coalesced;
     uint32_t period;
     QEMUTimer *coalesced_timer;
@@ -180,6 +183,8 @@ static void rtc_periodic_timer(void *opaque)
         s->cmos_data[RTC_REG_C] |= 0xc0;
 #ifdef TARGET_I386
         if(rtc_td_hack) {
+            if (s->irq_reinject_on_ack_count >= RTC_REINJECT_ON_ACK_COUNT)
+                s->irq_reinject_on_ack_count = 0;              
             apic_reset_irq_delivered();
             rtc_irq_raise(s->irq);
             if (!apic_get_irq_delivered()) {
@@ -458,6 +463,18 @@ static uint32_t cmos_ioport_read(void *opaque, uint32_t addr)
         case RTC_REG_C:
             ret = s->cmos_data[s->cmos_index];
             qemu_irq_lower(s->irq);
+#ifdef TARGET_I386
+            if(s->irq_coalesced &&
+                    s->irq_reinject_on_ack_count < RTC_REINJECT_ON_ACK_COUNT) {
+                s->irq_reinject_on_ack_count++;
+                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: