[patch 24/48] KVM: SVM: Remove port 80 passthrough

From: Greg KH
Date: Fri Sep 04 2009 - 16:20:03 EST

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

From: Avi Kivity <avi@xxxxxxxxxx>

(cherry picked from commit 99f85a28a78e96d28907fe036e1671a218fee597)

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

Remove the port passthrough to avoid the problem.

Reported-by: Piotr JaroszyÅ?ski <p.jaroszynski@xxxxxxxxx>
Tested-by: Piotr JaroszyÅ?ski <p.jaroszynski@xxxxxxxxx>
Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
arch/x86/kvm/svm.c | 1 -
1 file changed, 1 deletion(-)

--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -429,7 +429,6 @@ 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))

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