KVM: x86: Sysexit emulation does not mask RIP/RSP

If the operand size is not 64-bit, then the sysexit instruction should assign
ECX to RSP and EDX to RIP.  The current code assigns the full 64-bits.

Fix it by masking.
Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/emulate.c

@@ -2417,6 +2417,8 @@ static int em_sysexit(struct x86_emulate_ctxt *ctxt)
 		if ((msr_data & 0xfffc) == 0x0)
 			return emulate_gp(ctxt, 0);
 		ss_sel = (u16)(msr_data + 24);
+		rcx = (u32)rcx;
+		rdx = (u32)rdx;
 		break;
 	case X86EMUL_MODE_PROT64:
 		cs_sel = (u16)(msr_data + 32);