KVM: fix emulator_task_switch() return value.

emulator_task_switch() should return -1 for failure and 0 for success to
the caller, just like x86_emulate_insn() does.
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/x86/kvm/emulate.c

@@ -2453,7 +2453,7 @@ int emulator_task_switch(struct x86_emulate_ctxt *ctxt,
 		rc = writeback(ctxt, ops);
 	}
 
-	return rc;
+	return (rc == X86EMUL_UNHANDLEABLE) ? -1 : 0;
 }
 
 static void string_addr_inc(struct x86_emulate_ctxt *ctxt, unsigned long base,

arch/x86/kvm/x86.c

@@ -4800,10 +4800,11 @@ int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int reason,
 				   tss_selector, reason, has_error_code,
 				   error_code);
 
-	if (ret == X86EMUL_CONTINUE)
-		kvm_x86_ops->set_rflags(vcpu, vcpu->arch.emulate_ctxt.eflags);
+	if (ret)
+		return EMULATE_FAIL;
 
-	return (ret != X86EMUL_CONTINUE);
+	kvm_x86_ops->set_rflags(vcpu, vcpu->arch.emulate_ctxt.eflags);
+	return EMULATE_DONE;
 }
 EXPORT_SYMBOL_GPL(kvm_task_switch);