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>

diff --git a/drivers/kvm/x86_emulate.c b/drivers/kvm/x86_emulate.c
index 9f8d59a..3be506a 100644 (file)
--- 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;