KVM: x86 emulator: address size and operand size overrides are sticky

Current implementation is to toggle, which is incorrect.  Patch ported from
corresponding Xen code.

Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 12 insertions, 7 deletions

diff --git a/drivers/kvm/x86_emulate.c b/drivers/kvm/x86_emulate.c
index 9f8d59a49313..3be506ac01a3 100644
--- a/drivers/kvm/x86_emulate.c
+++ b/drivers/kvm/x86_emulate.c
@@ -758,6 +758,7 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
         struct decode_cache *c = &ctxt->decode;
         int rc = 0;
         int mode = ctxt->mode;
+        int def_op_bytes, def_ad_bytes;
 
         /* Shadow copy of register state. Committed on successful emulation. */
 
@@ -768,34 +769,38 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
         switch (mode) {
         case X86EMUL_MODE_REAL:
         case X86EMUL_MODE_PROT16:
-                c->op_bytes = c->ad_bytes = 2;
+                def_op_bytes = def_ad_bytes = 2;
                 break;
         case X86EMUL_MODE_PROT32:
-                c->op_bytes = c->ad_bytes = 4;
+                def_op_bytes = def_ad_bytes = 4;
                 break;
 #ifdef CONFIG_X86_64
         case X86EMUL_MODE_PROT64:
-                c->op_bytes = 4;
-                c->ad_bytes = 8;
+                def_op_bytes = 4;
+                def_ad_bytes = 8;
                 break;
 #endif
         default:
                 return -1;
         }
 
+        c->op_bytes = def_op_bytes;
+        c->ad_bytes = def_ad_bytes;
+
         /* Legacy prefixes. */
         for (;;) {
                 switch (c->b = insn_fetch(u8, 1, c->eip)) {
                 case 0x66:      /* operand-size override */
-                        c->op_bytes ^= 6;       /* switch between 2/4 bytes */
+                        /* switch between 2/4 bytes */
+                        c->op_bytes = def_op_bytes ^ 6;
                         break;
                 case 0x67:      /* address-size override */
                         if (mode == X86EMUL_MODE_PROT64)
                                 /* switch between 4/8 bytes */
-                                c->ad_bytes ^= 12;
+                                c->ad_bytes = def_ad_bytes ^ 12;
                         else
                                 /* switch between 2/4 bytes */
-                                c->ad_bytes ^= 6;
+                                c->ad_bytes = def_ad_bytes ^ 6;
                         break;
                 case 0x2e:      /* CS override */
                         c->override_base = &ctxt->cs_base;