KVM: x86 emulator: fix access registers for instructions with ModR/M byte and Mod = 3

The patch belows changes the access type to register from memory for
instructions that are declared as SrcMem or DstMem, but have a
ModR/M byte with Mod = 3.

It fixes (at least) the lmsw and smsw instructions on an AMD64 CPU,
which are needed for FreeBSD.

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/drivers/kvm/x86_emulate.c b/drivers/kvm/x86_emulate.c
index 0a8696d9b82c..a6ace302e0cd 100644
--- a/drivers/kvm/x86_emulate.c
+++ b/drivers/kvm/x86_emulate.c
@@ -825,6 +825,14 @@ done_prefixes:
                 if (twobyte && b == 0x01 && modrm_reg == 7)
                         break;
               srcmem_common:
+                /*
+                 * For instructions with a ModR/M byte, switch to register
+                 * access if Mod = 3.
+                 */
+                if ((d & ModRM) && modrm_mod == 3) {
+                        src.type = OP_REG;
+                        break;
+                }
                 src.type = OP_MEM;
                 src.ptr = (unsigned long *)cr2;
                 src.val = 0;
@@ -893,6 +901,14 @@ done_prefixes:
                 dst.ptr = (unsigned long *)cr2;
                 dst.bytes = (d & ByteOp) ? 1 : op_bytes;
                 dst.val = 0;
+                /*
+                 * For instructions with a ModR/M byte, switch to register
+                 * access if Mod = 3.
+                 */
+                if ((d & ModRM) && modrm_mod == 3) {
+                        dst.type = OP_REG;
+                        break;
+                }
                 if (d & BitOp) {
                         unsigned long mask = ~(dst.bytes * 8 - 1);