KVM: x86 emulator: fix smsw and lmsw with a memory operand

lmsw and smsw were implemented only with a register operand.  Extend them
to support a memory operand as well.  Fixes Windows running some display
compatibility test on AMD hosts.

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

1 files changed, 17 insertions, 12 deletions

diff --git a/arch/x86/kvm/x86_emulate.c b/arch/x86/kvm/x86_emulate.c
index 8e1b32f2cd5e..46ef78f8bb35 100644
--- a/arch/x86/kvm/x86_emulate.c
+++ b/arch/x86/kvm/x86_emulate.c
@@ -275,12 +275,15 @@ static u16 group_table[] = {
         SrcMem | ModRM, 0, SrcMem | ModRM | Stack, 0,
         [Group7*8] =
         0, 0, ModRM | SrcMem, ModRM | SrcMem,
-        SrcNone | ModRM | DstMem, 0, SrcMem | ModRM, SrcMem | ModRM | ByteOp,
+        SrcNone | ModRM | DstMem | Mov, 0,
+        SrcMem16 | ModRM | Mov, SrcMem | ModRM | ByteOp,
 };
 
 static u16 group2_table[] = {
         [Group7*8] =
-        SrcNone | ModRM, 0, 0, 0, SrcNone | ModRM | DstMem, 0, SrcMem | ModRM, 0,
+        SrcNone | ModRM, 0, 0, 0,
+        SrcNone | ModRM | DstMem | Mov, 0,
+        SrcMem16 | ModRM | Mov, 0,
 };
 
 /* EFLAGS bit definitions. */
@@ -1722,6 +1725,8 @@ twobyte_insn:
                                 goto done;
 
                         kvm_emulate_hypercall(ctxt->vcpu);
+                        /* Disable writeback. */
+                        c->dst.type = OP_NONE;
                         break;
                 case 2: /* lgdt */
                         rc = read_descriptor(ctxt, ops, c->src.ptr,
@@ -1729,6 +1734,8 @@ twobyte_insn:
                         if (rc)
                                 goto done;
                         realmode_lgdt(ctxt->vcpu, size, address);
+                        /* Disable writeback. */
+                        c->dst.type = OP_NONE;
                         break;
                 case 3: /* lidt/vmmcall */
                         if (c->modrm_mod == 3 && c->modrm_rm == 1) {
@@ -1744,27 +1751,25 @@ twobyte_insn:
                                         goto done;
                                 realmode_lidt(ctxt->vcpu, size, address);
                         }
+                        /* Disable writeback. */
+                        c->dst.type = OP_NONE;
                         break;
                 case 4: /* smsw */
-                        if (c->modrm_mod != 3)
-                                goto cannot_emulate;
-                        *(u16 *)&c->regs[c->modrm_rm]
-                                = realmode_get_cr(ctxt->vcpu, 0);
+                        c->dst.bytes = 2;
+                        c->dst.val = realmode_get_cr(ctxt->vcpu, 0);
                         break;
                 case 6: /* lmsw */
-                        if (c->modrm_mod != 3)
-                                goto cannot_emulate;
-                        realmode_lmsw(ctxt->vcpu, (u16)c->modrm_val,
-                                                  &ctxt->eflags);
+                        realmode_lmsw(ctxt->vcpu, (u16)c->src.val,
+                                      &ctxt->eflags);
                         break;
                 case 7: /* invlpg*/
                         emulate_invlpg(ctxt->vcpu, memop);
+                        /* Disable writeback. */
+                        c->dst.type = OP_NONE;
                         break;
                 default:
                         goto cannot_emulate;
                 }
-                /* Disable writeback. */
-                c->dst.type = OP_NONE;
                 break;
         case 0x06:
                 emulate_clts(ctxt->vcpu);