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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 B10BBC433DF for ; Tue, 2 Jun 2020 12:42:02 +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 8D96520679 for ; Tue, 2 Jun 2020 12:42:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8D96520679 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1jg6EY-00014T-Ll; Tue, 02 Jun 2020 12:41:34 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1jg6EY-00014M-2Q for xen-devel@lists.xenproject.org; Tue, 02 Jun 2020 12:41:34 +0000 X-Inumbo-ID: 6369f3bc-a4ce-11ea-abea-12813bfff9fa Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 6369f3bc-a4ce-11ea-abea-12813bfff9fa; Tue, 02 Jun 2020 12:41:33 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 7614EAA7C; Tue, 2 Jun 2020 12:41:34 +0000 (UTC) Subject: Re: [PATCH v2 03/14] x86/shstk: Introduce Supervisor Shadow Stack support To: Anthony PERARD References: <20200527191847.17207-1-andrew.cooper3@citrix.com> <20200527191847.17207-4-andrew.cooper3@citrix.com> <4f535d4c-b3b3-fe5b-8b57-af736dc0a360@suse.com> <20200602122614.GN2105@perard.uk.xensource.com> From: Jan Beulich Message-ID: <3328fabd-c133-00a9-2ec0-addcf15dbff5@suse.com> Date: Tue, 2 Jun 2020 14:41:30 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.8.1 MIME-Version: 1.0 In-Reply-To: <20200602122614.GN2105@perard.uk.xensource.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Andrew Cooper , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , Wei Liu , Xen-devel Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 02.06.2020 14:26, Anthony PERARD wrote: > On Tue, Jun 02, 2020 at 02:06:11PM +0200, Jan Beulich wrote: >> I don't recall; perhaps I was in another parallel session? If it's >> the one with notes at >> https://lists.xenproject.org/archives/html/xen-devel/2019-07/msg00786.html >> then a remark close to the top suggests I was there, but there's no >> sign of this aspect having got discussed. There is, among the issues >> listed, "Xen build re-evaluates compiler support for every translation >> unit", but that's only remotely related. > > What is a "translation unit"? What would that have to do with Kconfig? A translation unit is the collective input from all source and header files seen by the compiler during the processing of one top level input file's worth of compilation. The connection to Kconfig here is that by switching to it, the compiler flags don't get re-constructed once per CU. Of course doing it via Kconfig is not the only possible solution to the problem (as can be seen from the patch that I had intermediately submitted to get at least the HAVE_AS_* out of that set), but for us the change in behavior is one intended (side-)effect of the switch to newer Kconfig. Jan