[patch 43/51] KVM: SVM: Remove port 80 passthrough

Greg KH
2009-05-14T22:57:12Z

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2.6.29-stable review patch. If anyone has any objections, please let us know.

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From: Avi Kivity <avi@redhat.com>

commit 99f85a28a78e96d28907fe036e1671a218fee597 upstream.

KVM optimizes guest port 80 accesses by passthing them through to the host.
Some AMD machines die on port 80 writes, allowing the guest to hard-lock the
host.

Remove the port passthrough to avoid the problem.

Reported-by: Piotr Jaroszyński <p.jaroszynski@gmail.com>
Tested-by: Piotr Jaroszyński <p.jaroszynski@gmail.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
arch/x86/kvm/svm.c | 1 -
1 file changed, 1 deletion(-)

--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -411,7 +411,6 @@ static __init int svm_hardware_setup(voi

iopm_va = page_address(iopm_pages);
memset(iopm_va, 0xff, PAGE_SIZE * (1 << IOPM_ALLOC_ORDER));
- clear_bit(0x80, iopm_va); /* allow direct access to PC debug port */
iopm_base = page_to_pfn(iopm_pages) << PAGE_SHIFT;

if (boot_cpu_has(X86_FEATURE_NX))