KVM: x86 emulator: implement 'ret far' instruction (opcode 0xcb)

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

1 files changed, 25 insertions, 1 deletions

diff --git a/arch/x86/kvm/x86_emulate.c b/arch/x86/kvm/x86_emulate.c
index 94459f313f12..ca91749d2083 100644
--- a/arch/x86/kvm/x86_emulate.c
+++ b/arch/x86/kvm/x86_emulate.c
@@ -178,7 +178,7 @@ static u32 opcode_table[256] = {
         0, ImplicitOps | Stack, 0, 0,
         ByteOp | DstMem | SrcImm | ModRM | Mov, DstMem | SrcImm | ModRM | Mov,
         /* 0xC8 - 0xCF */
-        0, 0, 0, 0, 0, 0, 0, 0,
+        0, 0, 0, ImplicitOps | Stack, 0, 0, 0, 0,
         /* 0xD0 - 0xD7 */
         ByteOp | DstMem | SrcImplicit | ModRM, DstMem | SrcImplicit | ModRM,
         ByteOp | DstMem | SrcImplicit | ModRM, DstMem | SrcImplicit | ModRM,
@@ -1278,6 +1278,25 @@ static inline int emulate_grp9(struct x86_emulate_ctxt *ctxt,
         return 0;
 }
 
+static int emulate_ret_far(struct x86_emulate_ctxt *ctxt,
+                           struct x86_emulate_ops *ops)
+{
+        struct decode_cache *c = &ctxt->decode;
+        int rc;
+        unsigned long cs;
+
+        rc = emulate_pop(ctxt, ops, &c->eip, c->op_bytes);
+        if (rc)
+                return rc;
+        if (c->op_bytes == 4)
+                c->eip = (u32)c->eip;
+        rc = emulate_pop(ctxt, ops, &cs, c->op_bytes);
+        if (rc)
+                return rc;
+        rc = kvm_load_segment_descriptor(ctxt->vcpu, (u16)cs, 1, VCPU_SREG_CS);
+        return rc;
+}
+
 static inline int writeback(struct x86_emulate_ctxt *ctxt,
                             struct x86_emulate_ops *ops)
 {
@@ -1735,6 +1754,11 @@ special_insn:
         mov:
                 c->dst.val = c->src.val;
                 break;
+        case 0xcb:              /* ret far */
+                rc = emulate_ret_far(ctxt, ops);
+                if (rc)
+                        goto done;
+                break;
         case 0xd0 ... 0xd1:     /* Grp2 */
                 c->src.val = 1;
                 emulate_grp2(ctxt);