KVM: x86 emulator: preserve an operand's segment identity

Currently the x86 emulator converts the segment register associated with
an operand into a segment base which is added into the operand address.
This loss of information results in us not doing segment limit checks properly.

Replace struct operand's addr.mem field by a segmented_address structure
which holds both the effetive address and segment.  This will allow us to
do the limit check at the point of access.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/x86/include/asm/kvm_emulate.h

@@ -159,7 +159,10 @@ struct operand {
 	};
 	union {
 		unsigned long *reg;
-		unsigned long mem;
+		struct segmented_address {
+			ulong ea;
+			unsigned seg;
+		} mem;
 	} addr;
 	union {
 		unsigned long val;