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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 85660C433EF for ; Fri, 3 Sep 2021 08:40:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5FDD9610CC for ; Fri, 3 Sep 2021 08:40:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348336AbhICIlg (ORCPT ); Fri, 3 Sep 2021 04:41:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43296 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348379AbhICIla (ORCPT ); Fri, 3 Sep 2021 04:41:30 -0400 Received: from sipsolutions.net (s3.sipsolutions.net [IPv6:2a01:4f8:191:4433::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B876CC061575 for ; Fri, 3 Sep 2021 01:40:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sipsolutions.net; s=mail; h=Content-Transfer-Encoding:MIME-Version: Content-Type:References:In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender :Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From:Resent-To: Resent-Cc:Resent-Message-ID; bh=wBj6nos2hDwqH7CVknKIIQQxUxx9v/M+OP/YK2wBbOc=; t=1630658430; x=1631868030; b=Fe49fPp27uhD/qX5pw0kfudx/2F/OEJfPPSUuESgK553FRr jYUhdO1n89SDgZNK5FWOfZ0p1WZ87KMwFlgSlj3htepJlkQmyp7T2jCUAD+Dqb9YuvjgZ1g4M/G8o WbKY+FLVXMmG0x1VmH711nrMmEepwiQ0SHNSK5+yZzt5rS0317dSD+277nyPk6gPg/yn0XZDy7iiR szlo3Rfznm6UREmORbHYuv9ykaiqftspxXkZBubZbj0xPi909IU50AlIeZPt7NOMg8m0E/+GEZvS2 c4skFqTs4DEIjfrLgkWKlhGcAj0Dojd7FQFqe+iDkEGeDTfIzTcjNhZMNHtqGUuQ==; Received: by sipsolutions.net with esmtpsa (TLS1.3:ECDHE_SECP256R1__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.94.2) (envelope-from ) id 1mM4kK-001zew-4n; Fri, 03 Sep 2021 10:40:24 +0200 Message-ID: <30ab717a9ba1c2bb17e2a6948ff61d26c4430772.camel@sipsolutions.net> Subject: Re: [PATCH] um: don't use CONFIG_X86_{32,64} symbols on x86 From: Johannes Berg To: David Laight , "linux-um@lists.infradead.org" Cc: "x86@kernel.org" , "linux-kernel@vger.kernel.org" Date: Fri, 03 Sep 2021 10:40:23 +0200 In-Reply-To: References: <20210902102750.1ddfef4c1915.Icb5c49998c55b87c8584d46894c01b114ae2e661@changeid> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.38.4 (3.38.4-1.fc33) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-malware-bazaar: not-scanned Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2021-09-03 at 08:27 +0000, David Laight wrote: > From: Johannes Berg > > Sent: 02 September 2021 09:28 > > > > The CONFIG_X86_32 and CONFIG_X86_64 symbols are used by > > both "real" x86 architecture builds and ARCH=um today. > > However, clearly most people and places in the code are > > treating it as the architecture Kconfig (technically > > that's just CONFIG_X86) and use it to indicate that the > > architecture is X86 in 32- or 64-bit flavour. > > > > This has caused a fair amount of issues in the past, > > for example drivers not building because use x86 macros > > or similar under CONFIG_X86_{32,64} ifdef, and then we > > find build reports and add "!UML" to their Kconfig etc. > > > > However, this is error-prone and a kind of whack-a-mole > > game, even with the build bots reporting things. > > I suspect you've just changed the 'mole'. Yeah, that thought occurred to me too. > You've now got lots of lines like: > > #if defined(CONFIG_X86_64) || defined(CONFIG_X86_64_UML) > > Missing off the UML define is going to cause the 32bit code > to get compiled by mistake - which is likely to be more > confusing that the places where you need to do special 'stuff' > for UML I'm not sure I agree though. Yes, I agree that I have a number of lines. But looking through them, we have new ones: - AFS, and it fundamentally wants to know the arch. If it misses one, well, that can also happen with any other arch. - XFS/falloc has arch-specific stuff again, and considers other architectures too - fs/ioctl.c is actually unnecessary since CONFIG_COMPAT doesn't exist on UML - same for blktrace - BPF jit - not really sure about that one - crypto Kconfig - but again already considers different architectures there - sound - ok that's a stupid one :) - lzo - again stuff that already considers many architectures But on the other side removal we have - sysctl - netfilter - security - many fixes to driver Kconfig that you don't see here because they're *missing* "depends on !UML" now So my gut feeling is that while we've indeed traded one mole for another in a sense, the somewhat surprising places (like sound and BPF) are much fewer, and most of the places that we now need it are places that are already considering different architectures. johannes