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=-12.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 D1B69C433E0 for ; Thu, 11 Mar 2021 09:31:37 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 50DED64F95 for ; Thu, 11 Mar 2021 09:31:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 50DED64F95 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=xen.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.96404.182330 (Exim 4.92) (envelope-from ) id 1lKHf9-00061S-7E; Thu, 11 Mar 2021 09:31:23 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 96404.182330; Thu, 11 Mar 2021 09:31:23 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lKHf9-00061L-3v; Thu, 11 Mar 2021 09:31:23 +0000 Received: by outflank-mailman (input) for mailman id 96404; Thu, 11 Mar 2021 09:31:21 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lKHf7-00061G-N7 for xen-devel@lists.xenproject.org; Thu, 11 Mar 2021 09:31:21 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lKHf6-0001m0-Ee; Thu, 11 Mar 2021 09:31:20 +0000 Received: from 54-240-197-224.amazon.com ([54.240.197.224] helo=a483e7b01a66.ant.amazon.com) by xenbits.xenproject.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1lKHf6-0006bK-2I; Thu, 11 Mar 2021 09:31:20 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xen.org; s=20200302mail; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:Cc:To:Subject; bh=xUgZGw0PM4aGrq8PRtjULlOHasMLa7vf5FqAOS9c090=; b=Z1InrgFn0c/VuJkl8vgtgAEp6n fptAdbsD7gr/8IoOABFA/Qi34oMiek0fh5tXb6N20TTUDBudWQF2yzpGw9uGqC5TgxYrdi0rceGxn h9rrV3PK2tKG+knzmAGCC2nZkdaH8yyKzdBUip33PFECfpBEDpoHjGYVgKjc64idrsPY=; Subject: Re: [PATCH for-4.15] xen: Bump the minimum version of GCC supported to 4.9 (5.1 on arm64) To: Jan Beulich Cc: Julien Grall , Andrew Cooper , George Dunlap , Ian Jackson , Stefano Stabellini , Wei Liu , xen-devel@lists.xenproject.org References: <20210306214148.27021-1-julien@xen.org> <1897022d-7591-3450-4e57-884a2860b13d@suse.com> <7fd07dc9-9c03-bb13-3907-c3c268a4e970@xen.org> <2de5160f-8636-5cdf-a20c-acaa2640c893@suse.com> <7ab87cab-8836-e8a0-993e-0cdeca3c45e3@xen.org> <2bc2ad13-8636-e5d4-3a4a-722c75e3b92a@suse.com> From: Julien Grall Message-ID: <6048b3f0-b131-9ced-9521-a935e5b337eb@xen.org> Date: Thu, 11 Mar 2021 09:31:17 +0000 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: <2bc2ad13-8636-e5d4-3a4a-722c75e3b92a@suse.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Hi Jan, On 11/03/2021 08:17, Jan Beulich wrote: > On 10.03.2021 19:05, Julien Grall wrote: >> On 09/03/2021 11:20, Jan Beulich wrote: >>> On 08.03.2021 21:22, Julien Grall wrote: >>>> On 08/03/2021 11:20, Jan Beulich wrote: >>>>> On 08.03.2021 11:51, Julien Grall wrote: >>>>>> On 08/03/2021 08:09, Jan Beulich wrote: >>>>>>> Additionally - partly related to your own reply regarding the CI >>>>>>> failures - imo there needs to be an analysis of what older distros >>>>>>> will no longer build (at all or by default). >>>>>> >>>>>> Per the CI, this would be Ubuntu Trusty (and older), Centos 7 (and older) >>>>>> >>>>>> Do you have any other in mind? >>>>> >>>>> Our SLE12 (latest service pack is SP5 and still has a while to go >>>>> to at least reach LTSS state) comes with gcc 4.8 as the default >>>>> compiler. >>>> >>>> Thanks! That's good to know. Is it the old GCC Suse supports? >>> >>> Not sure I understand the question: The default compiler of this or >>> any distro is of course (expected to be) supported by the vendor >>> for the lifetime of the OS. >> >> Sorry for the wording. I was asking whether Suse also supports compiler >> older than GCC 4.8. > > Oh, I see. SLES11 has another year to go for LTSS to end, and it's 4.3 > which is used there. Thanks for the info! Are you planning to build Xen 4.15 there too? > >>>>>>>> --- a/xen/include/xen/compiler.h >>>>>>>> +++ b/xen/include/xen/compiler.h >>>>>>>> @@ -5,6 +5,19 @@ >>>>>>>> #error Sorry, your compiler is too old/not recognized. >>>>>>>> #endif >>>>>>>> >>>>>>>> +#if CONFIG_CC_IS_GCC >>>>>>>> +# if CONFIG_GCC_VERSION < 40900 >>>>>>>> +/* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145 */ >>>>>>> >>>>>>> As per the bug report, the issue was determined to not be present >>>>>>> in e.g. 4.3. Hence while such a bug may influence our choice of >>>>>>> minimum version, I don't think it can reasonably be named here as >>>>>>> the apparent only reason for the choice. Personally I don't think >>>>>>> any justification should be put here. >>>>>> >>>>>> Ok. >>>>>> >>>>>>> >>>>>>>> +# error Sorry, your version of GCC is too old - please use 4.9 or newer. >>>>>>>> +# elif defined(CONFIG_ARM_64) && CONFIG_GCC_VERSION < 50100 >>>>>>>> +/* >>>>>>>> + * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63293 >>>>>>>> + * https://lore.kernel.org/r/20210107111841.GN1551@shell.armlinux.org.uk >>>>>>>> + */ >>>>>>>> +# error Sorry, your version of GCC is too old - please use 5.1 or newer. >>>>>>> >>>>>>> From the bug entry the fix looks to have been backported to 4.9, >>>>>>> or at least some (important?) branches thereof. >>>>>> >>>>>> It is not clear what's you are trying to point out. Mind clarifying? >>>>> >>>>> Some 4.9 compilers (perhaps widely used ones) may not have the bad >>>>> issue, which puts under question their ruling out when the main >>>>> reason for doing so is that bug. >>>> >>>> Well... We could surely try to hunt which GCC 4.9 has been fixed. But I >>>> am not convinced this is useful, we would need to have an allowlist of >>>> GCC compiler. >>> >>> Or probe the compiler for the bug in question. >> >> I thought about it but it is not clear to me whether the reproducer >> would work on every GCC version and how to detect that this was miscompiled. >> >> Do you have any suggestion? > > To have one I'd have to study the problem in quite a bit more detail. > But I did say that what you do for Arm is largely up to you (and > Stefano did meanwhile ack the Arm side), so I'm not sure I want to > invest the time that would be needed. Well, there are still miscompilation problem on x86... So it would be good to have a way to address it. Anyway, I will split the Arm change in a separate patch so it can go in 4.15. Cheers, -- Julien Grall