[PATCH v2] KVM: IOAPIC: only access APIC registers one dword at a time

Xiao Guangrong
2010-07-02T08:00:12Z

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 | 20 +++++++-------------
1 files changed, 7 insertions(+), 13 deletions(-)

diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
index 1149c60..6610d11 100644
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -288,6 +288,11 @@ static int ioapic_mmio_read(struct kvm_io_device *this, gpa_t addr, int len,
ioapic_debug("addr %lx\n", (unsigned long)addr);
ASSERT(!(addr & 0xf)); /* check alignment */

+ if (len != 4) {
+ printk(KERN_WARNING "ioapic: wrong length %d\n", len);
+ return 0;
+ }
+
addr &= 0xff;
spin_lock(&ioapic->lock);
switch (addr) {
@@ -305,18 +310,7 @@ 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);
- break;
- default:
- printk(KERN_WARNING "ioapic: wrong length %d\n", len);
- }
+ *(u32 *) val = result;
return 0;
}

@@ -332,7 +326,7 @@ 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