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 EBE25C433EF for ; Tue, 10 May 2022 09:54:55 +0000 (UTC) Received: from localhost ([::1]:58804 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1noMZz-00079e-2V for qemu-devel@archiver.kernel.org; Tue, 10 May 2022 05:54:55 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:50588) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1noM4v-0005mj-02 for qemu-devel@nongnu.org; Tue, 10 May 2022 05:22:49 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:28557) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1noM4s-00007F-FH for qemu-devel@nongnu.org; Tue, 10 May 2022 05:22:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1652174565; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=iSMGMxuiYEqoVaETiVIQUbCcQsvvlBdY3AIWqh6a274=; b=MnLTMI7NpzNp2FPmV2aRPN+ORpoYax8xQ1HejLH0fv71uv5rOPYA6o1aur9Ucwfu2lYPAn gV+Sz+RFUCmKAkMogaTiuL45Ftr7/mcngGdzUbws/WJ3et7Is1jyZUDDyMr8hTokIaipax Fc+swQbjv3t6li3o6pl62ISJH88EVu0= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-577-UJaqAdTVOROMPQ5dMGqmGw-1; Tue, 10 May 2022 05:22:41 -0400 X-MC-Unique: UJaqAdTVOROMPQ5dMGqmGw-1 Received: by mail-wm1-f69.google.com with SMTP id q128-20020a1c4386000000b003942fe15835so5040306wma.6 for ; Tue, 10 May 2022 02:22:41 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=iSMGMxuiYEqoVaETiVIQUbCcQsvvlBdY3AIWqh6a274=; b=BrbDGTFNn2SbZLHDM7jGvrwH7pstkLKJHg75n2cEtOX6WAyaRkEMWjUAk5c8LTrZjm EMNSzBEPKzufdlWMicicFkoFaHsxfbO1FFKIVtgVuMXxxdr3gvNtGhuSatULY2tGmHAr DWkymLmUYaj2Y8UbMGBtA93EvVCfftW33v2LGHL0CwJ+hCrp3bOHFCBngd28v9s/NHm0 A5my2WlZ8FpJU2rk20GCEctqcelxW9fKy815aUjRtvcpa3eb3/57N/AQW44oQgcs0ppq H84H8JkLs3NsgY/x3Z6GOfKinL47jhzbui3RnIn9EjPopj3GCwHwR/gftitgEhnSFnOP Xlnw== X-Gm-Message-State: AOAM533Gjkg31mB1YLeCTPBCnb9GzydUydgW/dtgJfFS9eeXFB9aPQPk 9fwwhFjkKE+NOcDfwr+aXs0hX+pic2/+KGcTRiJAco874w3H1V0gidBu9aST7YDWMTMxoJuYyot XzeyX2NsGGrj59c8= X-Received: by 2002:a1c:7414:0:b0:394:1d5d:27f2 with SMTP id p20-20020a1c7414000000b003941d5d27f2mr20610039wmc.37.1652174560288; Tue, 10 May 2022 02:22:40 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzCk0GKV+j7ln5Pb9wycQvVEGl+hQN2zZ+MSJ3A6E9253bkQ85WKn40N7BKCUGOz/zp4M5yuQ== X-Received: by 2002:a1c:7414:0:b0:394:1d5d:27f2 with SMTP id p20-20020a1c7414000000b003941d5d27f2mr20610010wmc.37.1652174560041; Tue, 10 May 2022 02:22:40 -0700 (PDT) Received: from work-vm (cpc109025-salf6-2-0-cust480.10-2.cable.virginm.net. [82.30.61.225]) by smtp.gmail.com with ESMTPSA id l5-20020a5d5605000000b0020c5253d8d3sm13132928wrv.31.2022.05.10.02.22.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 May 2022 02:22:39 -0700 (PDT) Date: Tue, 10 May 2022 10:22:36 +0100 From: "Dr. David Alan Gilbert" To: Peter Maydell Cc: Thomas Huth , Markus Armbruster , qemu-devel@nongnu.org, qemu-arm , Richard Henderson , Mark Cave-Ayland , Fabiano Rosas , muriloo@linux.ibm.com, Paolo Bonzini , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= , Daniel Henrique Barboza , mopsfelder@gmail.com, qemu-ppc@nongnu.org, =?iso-8859-1?Q?C=E9dric?= Le Goater , qemu-RISC-V Subject: Re: QEMU 32-bit vs. 64-bit binaries Message-ID: References: <9ec244e0-4c7c-69ff-08f8-da451f6da449@linux.ibm.com> <87sfpqaey7.fsf@linux.ibm.com> <2ab9e2b3-5dba-4e18-ed2e-6063a2716f4c@ilande.co.uk> <87ilql9xww.fsf@linux.ibm.com> <472e45e8-319b-ad48-3afa-0dfa74e6ad20@redhat.com> <877d6tzs2e.fsf@pond.sub.org> <32e5877d-ba45-ac63-d24e-1f9f8676c6bb@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/2.2.1 (2022-02-19) Received-SPF: pass client-ip=170.10.129.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Peter Maydell (peter.maydell@linaro.org) wrote: > On Tue, 10 May 2022 at 10:01, Thomas Huth wrote: > > > > On 10/05/2022 10.54, Markus Armbruster wrote: > > > Thomas Huth writes: > > > > > > [...] > > > > > >> I once suggested in the past already that we should maybe get rid of > > >> the 32-bit variants in case the 64-bit variant is a full superset, so > > >> we can save compile- and test times (which is quite a bit for QEMU), > > >> but I've been told that the 32-bit variants are mostly still required > > >> for supporting KVM on 32-bit host machines. > > > > > > Do we still care for 32-bit host machines? > > > > As long as the Linux kernel still supports 32-bit KVM virtualization, I > > think we have to keep the userspace around for that, too. > > > > But I wonder why we're keeping qemu-system-arm around? 32-bit KVM support > > for ARM has been removed with Linux kernel 5.7 as far as I know, so I think > > we could likely drop the qemu-system-arm nowadays, too? Peter, Richard, > > what's your opinion on this? > > Two main reasons, I think: > * command-line compatibility (ie there are lots of > command lines out there using that binary name) > * nobody has yet cared enough to come up with a plan for what > we want to do differently for these 32-bit architectures, > so the default is "keep doing what we always have" > > In particular, I don't want to get rid of qemu-system-arm as the > *only* 32-bit target binary we drop. Either we stick with what > we have or we have a larger plan for sorting this out consistently > across target architectures. To my mind, qemu-system-arm makes a lot of sense, and I'd rather see the 32 bit guests disappear from qemu-system-aarch64. It's difficult to justify to someone running their aarch virt stack why their binary has the security footprint that includes a camera or PDA. ARM is a lot cleaner than x86; you don't suddenly find a little Cortex-M machine with a big 64 bit core in it; yet on x86 our machines are frankenstinian mixes with 25 year old chipsets and modern CPUs. Dave > -- PMM > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK