KVM: x86 emulator: implement CWD (opcode 99)

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

1 files changed, 14 insertions, 1 deletions

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 55849c3d5d8c..e257f2286866 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2280,6 +2280,18 @@ static int em_imul_3op(struct x86_emulate_ctxt *ctxt)
         return em_imul(ctxt);
 }
 
+static int em_cwd(struct x86_emulate_ctxt *ctxt)
+{
+        struct decode_cache *c = &ctxt->decode;
+
+        c->dst.type = OP_REG;
+        c->dst.bytes = c->src.bytes;
+        c->dst.addr.reg = &c->regs[VCPU_REGS_RDX];
+        c->dst.val = ~((c->src.val >> (c->src.bytes * 8 - 1)) - 1);
+
+        return X86EMUL_CONTINUE;
+}
+
 static int em_rdtsc(struct x86_emulate_ctxt *ctxt)
 {
         unsigned cpl = ctxt->ops->cpl(ctxt->vcpu);
@@ -2425,7 +2437,8 @@ static struct opcode opcode_table[256] = {
         /* 0x90 - 0x97 */
         X8(D(SrcAcc | DstReg)),
         /* 0x98 - 0x9F */
-        D(DstAcc | SrcNone), N, D(SrcImmFAddr | No64), N,
+        D(DstAcc | SrcNone), I(ImplicitOps | SrcAcc, em_cwd),
+        D(SrcImmFAddr | No64), N,
         D(ImplicitOps | Stack), D(ImplicitOps | Stack), N, N,
         /* 0xA0 - 0xA7 */
         D(ByteOp | DstAcc | SrcMem | Mov | MemAbs), D(DstAcc | SrcMem | Mov | MemAbs),