KVM: Allow aligned byte and word writes to IOAPIC registers.

This fixes byte accesses to IOAPIC_REG_SELECT as mandated by at least the
ICH10 and Intel Series 5 chipset specs. It also makes ioapic_mmio_write
consistent with ioapic_mmio_read, which also allows byte and word accesses.

Signed-off-by: Julian Stecklina <js@alien8.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
index 3eed61e..71e2253 100644 (file)
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -332,9 +332,18 @@ static int ioapic_mmio_write(struct kvm_io_device *this, gpa_t addr, int len,
                     (void*)addr, len, val);
        ASSERT(!(addr & 0xf));  /* check alignment */
 
-       if (len == 4 || len == 8)
+       switch (len) {
+       case 8:
+       case 4:
                data = *(u32 *) val;
-       else {
+               break;
+       case 2:
+               data = *(u16 *) val;
+               break;
+       case 1:
+               data = *(u8  *) val;
+               break;
+       default:
                printk(KERN_WARNING "ioapic: Unsupported size %d\n", len);
                return 0;
        }
@@ -343,7 +352,7 @@ static int ioapic_mmio_write(struct kvm_io_device *this, gpa_t addr, int len,
        spin_lock(&ioapic->lock);
        switch (addr) {
        case IOAPIC_REG_SELECT:
-               ioapic->ioregsel = data;
+               ioapic->ioregsel = data & 0xFF; /* 8-bit register */
                break;
 
        case IOAPIC_REG_WINDOW: