KVM: SVM: Allow direct guest access to PC debug port

The PC debug port is used for IO delay and does not require emulation.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/drivers/kvm/svm.c b/drivers/kvm/svm.c
index fa17d6d4f0cb..6cd6a50a0340 100644
--- a/drivers/kvm/svm.c
+++ b/drivers/kvm/svm.c
@@ -378,7 +378,7 @@ static __init int svm_hardware_setup(void)
         int cpu;
         struct page *iopm_pages;
         struct page *msrpm_pages;
-        void *msrpm_va;
+        void *iopm_va, *msrpm_va;
         int r;
 
         kvm_emulator_want_group7_invlpg();
@@ -387,8 +387,10 @@ static __init int svm_hardware_setup(void)
 
         if (!iopm_pages)
                 return -ENOMEM;
-        memset(page_address(iopm_pages), 0xff,
-                                        PAGE_SIZE * (1 << IOPM_ALLOC_ORDER));
+
+        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;