KVM: x86 emulator: fix regression with cmpxchg8b on i386 hosts

operand::val and operand::orig_val are 32-bit on i386, whereas cmpxchg8b
operands are 64-bit.

Fix by adding val64 and orig_val64 union members to struct operand, and
using them where needed.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index b38bd8b..66ca98a 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1870,17 +1870,16 @@
 			       struct x86_emulate_ops *ops)
 {
 	struct decode_cache *c = &ctxt->decode;
-	u64 old = c->dst.orig_val;
+	u64 old = c->dst.orig_val64;
 
 	if (((u32) (old >> 0) != (u32) c->regs[VCPU_REGS_RAX]) ||
 	    ((u32) (old >> 32) != (u32) c->regs[VCPU_REGS_RDX])) {
-
 		c->regs[VCPU_REGS_RAX] = (u32) (old >> 0);
 		c->regs[VCPU_REGS_RDX] = (u32) (old >> 32);
 		ctxt->eflags &= ~EFLG_ZF;
 	} else {
-		c->dst.val = ((u64)c->regs[VCPU_REGS_RCX] << 32) |
-		       (u32) c->regs[VCPU_REGS_RBX];
+		c->dst.val64 = ((u64)c->regs[VCPU_REGS_RCX] << 32) |
+			(u32) c->regs[VCPU_REGS_RBX];
 
 		ctxt->eflags |= EFLG_ZF;
 	}
@@ -2616,7 +2615,7 @@
 					c->src.valptr, c->src.bytes);
 		if (rc != X86EMUL_CONTINUE)
 			goto done;
-		c->src.orig_val = c->src.val;
+		c->src.orig_val64 = c->src.val64;
 	}
 
 	if (c->src2.type == OP_MEM) {