KVM: SVM: Remove port 80 passthrough

(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
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>

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 8233b86..77cae01 100644 (file)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -429,7 +429,6 @@ static __init int svm_hardware_setup(void)
 
        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))