KVM: SVM: Remove port 80 passthrough

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>

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index da568212966a07f7bb9cc2c8da44846836df5db3..dd8eeeae597964388e40799de9b6d92628761101 100644 (file)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -411,7 +411,6 @@ 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))