KVM: x86 emulator: Add std and cld instructions (opcodes 0xfc-0xfd)

This adds the std and cld instructions to the emulator.

Encountered while running the BIOS with invalid guest
state emulation enabled.

Signed-off-by: Mohammed Gamal <m.gamal005@gmail.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/arch/x86/kvm/x86_emulate.c b/arch/x86/kvm/x86_emulate.c
index 66e0bd6c628b..944f1f4d4be4 100644
--- a/arch/x86/kvm/x86_emulate.c
+++ b/arch/x86/kvm/x86_emulate.c
@@ -187,7 +187,7 @@ static u16 opcode_table[256] = {
         ImplicitOps, ImplicitOps, Group | Group3_Byte, Group | Group3,
         /* 0xF8 - 0xFF */
         ImplicitOps, 0, ImplicitOps, ImplicitOps,
-        0, 0, Group | Group4, Group | Group5,
+        ImplicitOps, ImplicitOps, Group | Group4, Group | Group5,
 };
 
 static u16 twobyte_table[256] = {
@@ -1762,6 +1762,14 @@ special_insn:
                 ctxt->eflags |= X86_EFLAGS_IF;
                 c->dst.type = OP_NONE;  /* Disable writeback. */
                 break;
+        case 0xfc: /* cld */
+                ctxt->eflags &= ~EFLG_DF;
+                c->dst.type = OP_NONE;  /* Disable writeback. */
+                break;
+        case 0xfd: /* std */
+                ctxt->eflags |= EFLG_DF;
+                c->dst.type = OP_NONE;  /* Disable writeback. */
+                break;
         case 0xfe ... 0xff:     /* Grp4/Grp5 */
                 rc = emulate_grp45(ctxt, ops);
                 if (rc != 0)