[PATCH v5 1/5] hpet 'driftfix': add hooks required to detect coalesced interrupts (x86 apic only)

[Ulrich Obergfell <uobergfe@redhat.com>]

'target_get_irq_delivered' and 'target_reset_irq_delivered' point
to functions that are called by update_irq() to detect coalesced
interrupts. Initially they point to stub functions which pretend
successful interrupt injection. apic code calls two registration
functions to replace the stubs with apic_get_irq_delivered() and
apic_reset_irq_delivered().

This change can be replaced if a generic feedback infrastructure to
track coalesced IRQs for periodic, clock providing devices becomes
available.

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
---
 hw/apic.c |    4 ++++
 hw/pc.h   |   13 +++++++++++++
 vl.c      |   13 +++++++++++++
 3 files changed, 30 insertions(+), 0 deletions(-)

diff --git a/hw/apic.c b/hw/apic.c
index a45b57f..94b1d15 100644
--- a/hw/apic.c
+++ b/hw/apic.c
@@ -17,6 +17,7 @@
  * License along with this library; if not, see <http://www.gnu.org/licenses/>
  */
 #include "hw.h"
+#include "pc.h"
 #include "apic.h"
 #include "ioapic.h"
 #include "qemu-timer.h"
@@ -1143,6 +1144,9 @@ static SysBusDeviceInfo apic_info = {
 
 static void apic_register_devices(void)
 {
+    register_target_get_irq_delivered(apic_get_irq_delivered);
+    register_target_reset_irq_delivered(apic_reset_irq_delivered);
+
     sysbus_register_withprop(&apic_info);
 }
 
diff --git a/hw/pc.h b/hw/pc.h
index bc8fcec..7511f28 100644
--- a/hw/pc.h
+++ b/hw/pc.h
@@ -7,6 +7,19 @@
 #include "fdc.h"
 #include "net.h"
 
+extern int (*target_get_irq_delivered)(void);
+extern void (*target_reset_irq_delivered)(void);
+
+static inline void register_target_get_irq_delivered(int (*func)(void))
+{
+    target_get_irq_delivered = func;
+}
+
+static inline void register_target_reset_irq_delivered(void (*func)(void))
+{
+    target_reset_irq_delivered = func;
+}
+
 /* PC-style peripherals (also used by other machines).  */
 
 /* serial.c */
diff --git a/vl.c b/vl.c
index 73e147f..456e320 100644
--- a/vl.c
+++ b/vl.c
@@ -232,6 +232,19 @@ const char *prom_envs[MAX_PROM_ENVS];
 const char *nvram = NULL;
 int boot_menu;
 
+static int target_get_irq_delivered_stub(void)
+{
+    return 1;
+}
+
+static void target_reset_irq_delivered_stub(void)
+{
+    return;
+}
+
+int (*target_get_irq_delivered)(void) = target_get_irq_delivered_stub;
+void (*target_reset_irq_delivered)(void) = target_reset_irq_delivered_stub;
+
 typedef struct FWBootEntry FWBootEntry;
 
 struct FWBootEntry {
-- 
1.6.2.5