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=-5.0 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 085D0C433F5 for ; Wed, 15 Sep 2021 09:11:35 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 85AE760F11 for ; Wed, 15 Sep 2021 09:11:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 85AE760F11 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:49284 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mQQx3-00076Y-E5 for qemu-devel@archiver.kernel.org; Wed, 15 Sep 2021 05:11:33 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:49818) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mQQrK-0001NE-5y for qemu-devel@nongnu.org; Wed, 15 Sep 2021 05:05:38 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:45906) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mQQrI-0005zm-36 for qemu-devel@nongnu.org; Wed, 15 Sep 2021 05:05:37 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1631696730; 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=FPqhrRbo5g3BvXLeOdr0SMj6MFLIYdR412ZBL+w1vMk=; b=ait/TKpBBle3pPeU+Z26DnNXrRHqB/BTP30vxUwu+oZFvDxDwaGOydsstPCFXfAfB9OY68 A8C1KmYM5XhJMJaUncG94frjJt99HreyaUkE9dzy+Ie899Uv9ntXkB/DRFtCpk0LzKopTJ jlV1boSOqYh1PcnPuOb5T8Yldj0lLnY= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-111-9No6J7jpP4KoNqZKTaAfow-1; Wed, 15 Sep 2021 05:05:26 -0400 X-MC-Unique: 9No6J7jpP4KoNqZKTaAfow-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 75B62802923; Wed, 15 Sep 2021 09:05:19 +0000 (UTC) Received: from redhat.com (unknown [10.39.194.233]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3226C196E2; Wed, 15 Sep 2021 09:05:14 +0000 (UTC) Date: Wed, 15 Sep 2021 10:05:11 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Subject: Re: Deprecate 32-bit hosts? (was: Re: [PULL 14/14] hw/arm/aspeed: Add Fuji machine type) Message-ID: References: <20210913161304.3805652-1-clg@kaod.org> <20210913161304.3805652-15-clg@kaod.org> <88c26520-6b87-e7a2-ac78-c1c92477c814@kaod.org> <1949e204-1bce-f15b-553b-1b42b41e3e08@linaro.org> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/2.0.7 (2021-05-04) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.398, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, 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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Peter Maydell , Thomas Huth , Samuel Thibault , Andrew Jeffery , Michael Tokarev , Richard Henderson , "qemu-devel@nongnu.org" , "Richard W.M. Jones" , "qemu-arm@nongnu.org" , Joel Stanley , Peter Delevoryas , Paolo Bonzini , Stefan Weil , =?utf-8?Q?C=C3=A9dric?= Le Goater Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Sep 15, 2021 at 10:51:56AM +0200, Philippe Mathieu-Daudé wrote: > On 9/15/21 10:37 AM, Daniel P. Berrangé wrote: > > On Wed, Sep 15, 2021 at 09:42:48AM +0200, Thomas Huth wrote: > >> On 14/09/2021 17.22, Richard Henderson wrote: > >>> On 9/14/21 5:26 AM, Peter Maydell wrote: > >>>> (2) RAM blocks should have a length that fits inside a > >>>>      signed 32-bit type on 32-bit hosts (at least I assume this > >>>>      is where the 2047MB limit is coming from; in theory this ought > >>>>      to be improveable but auditing the code for mishandling of > >>>>      RAMblock sizes to ensure we weren't accidentally stuffing > >>>>      their size into a signed 'long' somewhere would be kind > >>>>      of painful) > >>> > >>> Recalling that the win64 abi model is p64, i.e. 'long' is still 32-bit > >>> while pointers are 64-bit, how close do we think we are to this being > >>> fixed already? > >>> > >>>> Even if we did fix (2) we'd need to compromise on (3) > >>>> sometimes still -- if a board has 4GB of RAM that's > >>>> not going to fit in 32 bits regardless. But we would be > >>>> able to let boards with 2GB have 2GB. > >>> > >>> I'm not opposed to deprecating 32-bit hosts...  ;-) > >> > >> I think we should consider this again, indeed. Plain 32-bit CPUs are quite > >> seldom these days, aren't they? And I think we urgently need to decrease the > >> amount of things that we have to test and maintain in our CI and developer > >> branches... So is there still a really really compelling reason to keep > >> 32-bit host support alive? > > > > I think it probably depends on the architecture to some extent. > > > > i386 is possibly getting rare enough to consider dropping, though > > IIUC, KVM in the kernel still supports it. Would feel odd to drop > > it in QEMU if the kernel still thinks it is popular enough to keep > > KVM support. > > > > armv7 feels like it is relatively common as 64-bit didn't arrive > > in widespread use until relatively recent times compared to x86_64. > > KVM dropped armv7, but then hardware for that was never widespread, > > so armv7 was always TCG dominated > > > > Other 32-bit arches were/are always rare. > > While I could understand there are rare uses of system emulation on > 32-bit hosts, I still believe user-emulation is used, but would like > to be proven to the contrary. With that in mind, I'm not sure removing > sysemu on 32-bit hosts is worthful. Maybe we should ask distribution > maintainers first, then eventually poll the community? Or start with > a deprecation warning? Well Debian still supports arm7, i686, mips officially, and several more unofficially, so that's an easy answer from that side. Fedora only has arm7, having dropped i686 a while ago. I don't have insight into usage of QEMU on any platforms breakdown though. 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 :|