Implement irq override support for timer interrupts. This matches what
QEMU+BOCHS has been doing for the latest 8 months, and is also what
real hardware does.

Windows expects this according to Beth Kon.

Signed-off-by: Jes Sorensen <address@hidden>

---
 src/acpi.c    |   12 ++++++++++++
 src/mptable.c |   26 +++++++++++++++++++++++---
 src/util.h    |    3 +++
 3 files changed, 38 insertions(+), 3 deletions(-)

Index: seabios/src/acpi.c
===================================================================
--- seabios.orig/src/acpi.c
+++ seabios/src/acpi.c
@@ -331,6 +331,18 @@ build_madt(struct rsdt_descriptor_rev1 *
     io_apic->interrupt = cpu_to_le32(0);
 
     struct madt_intsrcovr *intsrcovr = (void*)&io_apic[1];
+
+    if (irq0override) {
+        memset(intsrcovr, 0, sizeof(*intsrcovr));
+        intsrcovr->type   = APIC_XRUPT_OVERRIDE;
+        intsrcovr->length = sizeof(*intsrcovr);
+        intsrcovr->source = 0;
+        intsrcovr->gsi    = 2;
+        intsrcovr->flags  = 0; /* conforms to bus specifications */
+        intsrcovr++;
+        madt_size += sizeof(struct madt_intsrcovr);
+    }
+
     for (i = 0; i < 16; i++) {
         if (!(PCI_ISA_IRQ_MASK & (1 << i)))
             /* No need for a INT source override structure. */
Index: seabios/src/mptable.c
===================================================================
--- seabios.orig/src/mptable.c
+++ seabios/src/mptable.c
@@ -10,6 +10,12 @@
 #include "config.h" // CONFIG_*
 #include "mptable.h" // MPTABLE_SIGNATURE
 
+#if CONFIG_KVM
+int irq0override = 1;
+#else
+int irq0override = 0;
+#endif
+
 void
 mptable_init(void)
 {
@@ -28,7 +34,10 @@ mptable_init(void)
                   + sizeof(struct mpt_cpu) * smp_cpus
                   + sizeof(struct mpt_bus)
                   + sizeof(struct mpt_ioapic)
-                  + sizeof(struct mpt_intsrc) * 16);
+                  + sizeof(struct mpt_intsrc) * 15);
+    if (!irq0override)
+        length += sizeof(struct mpt_intsrc);
+
     void *start = malloc_fseg(length);
     if (!start) {
         dprintf(1, "No room for MPTABLE!\n");
@@ -95,13 +104,24 @@ mptable_init(void)
 
     /* irqs */
     struct mpt_intsrc *intsrcs = (void *)&ioapic[1];
+    int j = 0;
     for(i = 0; i < 16; i++) {
-        struct mpt_intsrc *isrc = &intsrcs[i];
+        struct mpt_intsrc *isrc;
+        /* One entry per ioapic interrupt destination. Destination 2 is covered
+           by irq0->inti2 override (i == 0). Source IRQ 2 is unused */
+        if (irq0override && i == 2) {
+            j = 1;
+            continue;
+        }
+        isrc = &intsrcs[i - j];
         memset(isrc, 0, sizeof(*isrc));
         isrc->type = MPT_TYPE_INTSRC;
         isrc->srcbusirq = i;
         isrc->dstapic = ioapic_id;
-        isrc->dstirq = i;
+        if (irq0override && i == 0)
+	    isrc->dstirq = 2;
+        else
+	    isrc->dstirq = i;
     }
 
     // Set checksum.
Index: seabios/src/util.h
===================================================================
--- seabios.orig/src/util.h
+++ seabios/src/util.h
@@ -244,4 +244,7 @@ void reset_vector() __attribute__ ((nore
 // misc.c
 extern u8 BiosChecksum;
 
+// mptable.c
+extern int irq0override;
+
 #endif // util.h