[PATCH] KVM: IOAPIC: only access APIC registers one dword at a time

Xiao Guangrong
2010-07-02T04:42:24Z

The IOAPIC spec says:

When accessing these registers, accesses must be done one dword at a time.
For example, software should never access byte 2 from the Data register before
accessing bytes 0 and 1. The hardware will not attempt to recover from a bad
programming model in this case.

So, this patch removes other width access

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
virt/kvm/ioapic.c | 10 +++-------
1 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
index 1149c60..f96816f 100644
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -306,14 +306,10 @@ static int ioapic_mmio_read(struct kvm_io_device *this, gpa_t addr, int len,
spin_unlock(&ioapic->lock);

switch (len) {
- case 8:
- *(u64 *) val = result;
- break;
- case 1:
- case 2:
case 4:
- memcpy(val, (char *)&result, len);
+ *(u32 *) val = result;
break;
+
default:
printk(KERN_WARNING "ioapic: wrong length %d\n", len);
}
@@ -332,7 +328,7 @@ 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)
+ if (len == 4)
data = *(u32 *) val;
else {
printk(KERN_WARNING "ioapic: Unsupported size %d\n", len);
--
1.6.1.2