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 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E1A13C6379F for ; Wed, 22 Feb 2023 09:52:43 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pUlnH-0005zn-BS; Wed, 22 Feb 2023 04:52:11 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pUlnG-0005zc-4t for qemu-devel@nongnu.org; Wed, 22 Feb 2023 04:52:10 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pUlnE-0004GY-2f for qemu-devel@nongnu.org; Wed, 22 Feb 2023 04:52:09 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1677059527; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=fl9JzPfl65mLMKbclXhOrNg4Mp332faxUErjf6Huiko=; b=i2cYr00UrBM8vqwW6erwl2/vLyPqstEsazFQivj8oQb0bevImf82whAuBvfzbdkhWIXdAP zc8w8qkhKvQf/6yQm4QBzKII6oABeqsAyWSUdy9I3tddIvPdECW9GJ59wHbJPQeOZTcWlc +TmVjcbFyv7Bzg017hmO+CPUREMLsbw= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-639-gLnyaZcSMWGK-4RwPY-uGQ-1; Wed, 22 Feb 2023 04:52:03 -0500 X-MC-Unique: gLnyaZcSMWGK-4RwPY-uGQ-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 90356100F907; Wed, 22 Feb 2023 09:52:02 +0000 (UTC) Received: from redhat.com (unknown [10.33.36.70]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2BE60C15BA0; Wed, 22 Feb 2023 09:52:00 +0000 (UTC) Date: Wed, 22 Feb 2023 09:51:57 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Bernhard Beschow Cc: qemu-devel@nongnu.org, Alex =?utf-8?Q?Benn=C3=A9e?= , Peter Maydell , Thomas Huth , Stefan Hajnoczi , Richard Henderson , libvir-list@redhat.com, Paolo Bonzini , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Reinoud Zandijk , Ryo ONODERA , Brad Smith , Stefan Weil Subject: Re: [RFC PATCH] docs/about/deprecated: Deprecate 32-bit host systems Message-ID: References: <20230130114428.1297295-1-thuth@redhat.com> <87h6w7694t.fsf@linaro.org> <45EE5F9E-B9B8-4DA4-809E-A95FC618E7BE@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <45EE5F9E-B9B8-4DA4-809E-A95FC618E7BE@gmail.com> User-Agent: Mutt/2.2.9 (2022-11-12) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Wed, Feb 22, 2023 at 09:11:13AM +0000, Bernhard Beschow wrote: > > > Am 30. Januar 2023 20:45:47 UTC schrieb "Alex Bennée" : > > > >Daniel P. Berrangé writes: > > > >> On Mon, Jan 30, 2023 at 11:47:02AM +0000, Peter Maydell wrote: > >>> On Mon, 30 Jan 2023 at 11:44, Thomas Huth wrote: > >>> > > >>> > Testing 32-bit host OS support takes a lot of precious time during the QEMU > >>> > contiguous integration tests, and considering that many OS vendors stopped > >>> > shipping 32-bit variants of their OS distributions and most hardware from > >>> > the past >10 years is capable of 64-bit > >>> > >>> True for x86, not necessarily true for other architectures. > >>> Are you proposing to deprecate x86 32-bit, or all 32-bit? > >>> I'm not entirely sure about whether we're yet at a point where > >>> I'd want to deprecate-and-drop 32-bit arm host support. > >> > >> Do we have a feeling on which aspects of 32-bit cause us the support > >> burden ? The boring stuff like compiler errors from mismatched integer > >> sizes is mostly quick & easy to detect simply through a cross compile. > >> > >> I vaguely recall someone mentioned problems with atomic ops in the past, > >> or was it 128-bit ints, caused implications for the codebase ? > > > >Atomic operations on > TARGET_BIT_SIZE and cputlb when > >TCG_OVERSIZED_GUEST is set. Also the core TCG code and a bunch of the > >backends have TARGET_LONG_BITS > TCG_TARGET_REG_BITS ifdefs peppered > >throughout. > > Are there any plans or ideas to support 128 bit architectures > such as CHERI in the future? There is already a QEMU fork > implementing CHERI for RISC V [1]. Also ARM has developed an > experimental hardware implementation of CHERI within the Morello > project where Linaro is involved as well, although the QEMU > implementation is performed by the University of Cambridge [2]. If 128 bit hardware exists and has real world non-toy usage, then a request to support it in QEMU is essentially inevitable. > I'm asking because once we deeply bake in the assumption that > host size >= guest size then adding such architectures will > become much harder. Yep, that is a risk. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|