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>

diff --git a/arch/x86/kvm/x86_emulate.c b/arch/x86/kvm/x86_emulate.c
index 66e0bd6..944f1f4 100644 (file)
--- 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)