From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 41272C0044C for ; Wed, 31 Oct 2018 04:58:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E56CF20685 for ; Wed, 31 Oct 2018 04:58:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="eeWjaNnB" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E56CF20685 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=oracle.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729158AbeJaNzS (ORCPT ); Wed, 31 Oct 2018 09:55:18 -0400 Received: from userp2120.oracle.com ([156.151.31.85]:39464 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728908AbeJaNzS (ORCPT ); Wed, 31 Oct 2018 09:55:18 -0400 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.22/8.16.0.22) with SMTP id w9V4n7Nw182910; Wed, 31 Oct 2018 04:57:54 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=reply-to : subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2018-07-02; bh=UQ7wziBZBYuApOnmuB0hEtVdlPN6VQcE7Q3mVcT1+sI=; b=eeWjaNnB83gdFRLgkhYFSEvXkcppvUkSnBdTjndKEXWv2SKD6WHV/zLiAFKhU/1CcIbQ dH1j++uKUnugAVz25ek4RMm5HMaUf+gTo0ti5aPTLBORdq9KHZYLiQJPQefk7C83Ad0V YdKRFqXhxD6FI/ljmd2DxJ+AFhxW9ZvV2MoNHvwFcFrso9r448KjZY0FOmFHS6HCsgbh gEO9Yk+kSYxMHP+0emqtJw3WnzstBj15hl1+ugT3O9A7fF/4OfNmSFPy+otQAnm0Shsw hWSiE37skUAeh2a3TwfDKpyUEba56QNQXbxHCroKwBY2glzcLyOA8l+dkI9o2wyYJtBE yw== Received: from userv0022.oracle.com (userv0022.oracle.com [156.151.31.74]) by userp2120.oracle.com with ESMTP id 2ncgnr0bpk-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 31 Oct 2018 04:57:54 +0000 Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userv0022.oracle.com (8.14.4/8.14.4) with ESMTP id w9V4vmOd008432 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 31 Oct 2018 04:57:48 GMT Received: from abhmp0013.oracle.com (abhmp0013.oracle.com [141.146.116.19]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id w9V4vjcX005814; Wed, 31 Oct 2018 04:57:45 GMT Received: from [10.191.22.95] (/10.191.22.95) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 30 Oct 2018 21:57:45 -0700 Reply-To: zhenzhong.duan@oracle.com Subject: Re: [PATCH 1/3] retpolines: Only enable retpoline when compiler support it To: Peter Zijlstra Cc: Linux-Kernel , mingo@redhat.com, luto@kernel.org, konrad.wilk@oracle.com, dwmw@amazon.co.uk, tglx@linutronix.de, Srinivas REDDY Eeda , bp@suse.de, daniel@iogearbox.net, yamada.masahiro@socionext.com, michal.lkml@markovi.net, hpa@zytor.com References: <20181030083210.GA1459@hirez.programming.kicks-ass.net> From: Zhenzhong Duan Organization: Oracle Message-ID: Date: Wed, 31 Oct 2018 12:58:27 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20181030083210.GA1459@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=gbk; format=flowed Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9062 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=671 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1810310041 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018/10/30 16:32, Peter Zijlstra wrote: > On Mon, Oct 29, 2018 at 11:55:04PM -0700, Zhenzhong Duan wrote: >> Since retpoline capable compilers are widely available, make >> CONFIG_RETPOLINE hard depend on it. >> >> Change KBUILD to use CONFIG_RETPOLINE_SUPPORT to avoid conflict with >> CONFIG_RETPOLINE which is used by kernel. >> >> With all that stuff, the check of RETPOLINE is changed to >> CONFIG_RETPOLINE. > > So what happens when we select CONFIG_RETPOLINE but do not have > RETPOLINE_SUPPORT ? From a quick reading we'll silently build a > !retpoline kernel. I would expect a build failure. CONFIG_RETPOLINE is only defined when CONFIG_RETPOLINE_SUPPORT is selected. See below chunk. --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -221,9 +221,10 @@ KBUILD_CFLAGS += -Wno-sign-compare KBUILD_CFLAGS += -fno-asynchronous-unwind-tables # Avoid indirect branches in kernel to deal with Spectre -ifdef CONFIG_RETPOLINE +ifdef CONFIG_RETPOLINE_SUPPORT ifneq ($(RETPOLINE_CFLAGS),) - KBUILD_CFLAGS += $(RETPOLINE_CFLAGS) -DRETPOLINE + KBUILD_CFLAGS += $(RETPOLINE_CFLAGS) -DCONFIG_RETPOLINE + KBUILD_AFLAGS += -DCONFIG_RETPOLINE endif endif Thanks Zhenzhong