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    |   10 ++++++++++
 src/mptable.c |   16 +++++++++++++---
 2 files changed, 23 insertions(+), 3 deletions(-)

Index: seabios/src/acpi.c
===================================================================
--- seabios.orig/src/acpi.c
+++ seabios/src/acpi.c
@@ -440,6 +440,16 @@ void acpi_bios_init(void)
     io_apic->interrupt = cpu_to_le32(0);
 
     struct madt_intsrcovr *intsrcovr = (void*)&io_apic[1];
+
+    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
@@ -29,7 +29,7 @@ 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 (start + length > bios_table_end_addr) {
         dprintf(1, "No room for MPTABLE!\n");
         return;
@@ -96,13 +96,23 @@ 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];
+        /* One entry per ioapic interrupt destination. Destination 2 is covered
+           by irq0->inti2 override (i == 0). Source IRQ 2 is unused */
+        if (i == 2) {
+            j = 1;
+            continue;
+        }
+        struct mpt_intsrc *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 (i == 0)
+	    isrc->dstirq = 2;
+        else
+	    isrc->dstirq = i;
     }
 
     // Set checksum.