@@ -2667,14 +2667,33 @@ int emulate_instruction(struct kvm_vcpu *vcpu,
r = x86_decode_insn(&vcpu->arch.emulate_ctxt, &emulate_ops);
- /* Reject the instructions other than VMCALL/VMMCALL when
- * try to emulate invalid opcode */
+ /* Only allow emulation of specific instructions on #UD
+ * (namely VMMCALL, sysenter, sysexit, syscall)*/
c = &vcpu->arch.emulate_ctxt.decode;
- if ((emulation_type & EMULTYPE_TRAP_UD) &&
- (!(c->twobyte && c->b == 0x01 &&
- (c->modrm_reg == 0 || c->modrm_reg == 3) &&
- c->modrm_mod == 3 && c->modrm_rm == 1)))
- return EMULATE_FAIL;
+ if (emulation_type & EMULTYPE_TRAP_UD) {
+ if (!c->twobyte)
+ return EMULATE_FAIL;
+ switch (c->b) {
+ case 0x01: /* VMMCALL */
+ if (c->modrm_mod != 3 || c->modrm_rm != 1)
+ return EMULATE_FAIL;
+ break;
+ case 0x34: /* sysenter */
+ case 0x35: /* sysexit */
+ if (c->modrm_mod != 0 || c->modrm_rm != 0)
+ return EMULATE_FAIL;
+ break;
+ case 0x05: /* syscall */
+ if (c->modrm_mod != 0 || c->modrm_rm != 0)
+ return EMULATE_FAIL;
+ break;
+ default:
+ return EMULATE_FAIL;
+ }
+
+ if (!(c->modrm_reg == 0 || c->modrm_reg == 3))
+ return EMULATE_FAIL;
+ }
++vcpu->stat.insn_emulation;
if (r) {