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 9E30DC27C7B for ; Wed, 12 Jun 2024 15:10:32 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sHPbd-0001DY-QK; Wed, 12 Jun 2024 11:09:45 -0400 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 1sHPbd-0001B7-3T for qemu-devel@nongnu.org; Wed, 12 Jun 2024 11:09:45 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sHPba-0007mb-Uw for qemu-devel@nongnu.org; Wed, 12 Jun 2024 11:09:44 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1718204981; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=8C7xU84fp0Ag0ax6iKxw6zxMFqNkwL2sb7WAyhVTjqo=; b=fEmfj6EAwg763YFMdJQzmZe5Uz0hZINzblIfKH4QW2IhfIo7U7bS4WUA1EoyyCKVpcoRrs mIQBgiNeuf3/dSR0QEYKYH57FuHa5OzK+qQZcusDeNkln3pUO4TDiozRsoxMThFK8wrreC yQ/Oe4jqjL/O9jOj5jS+eQo+eCS4ULw= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-586-ihnidZo5PTSdDipPxY4_jA-1; Wed, 12 Jun 2024 11:09:37 -0400 X-MC-Unique: ihnidZo5PTSdDipPxY4_jA-1 Received: from mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.40]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 8304A1955E7E; Wed, 12 Jun 2024 15:09:36 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.115]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id B867019560AD; Wed, 12 Jun 2024 15:09:33 +0000 (UTC) Date: Wed, 12 Jun 2024 16:09:29 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Paolo Bonzini , Alexander Monakov , qemu-devel@nongnu.org, Richard Henderson Subject: Re: [PATCH 0/5] Reinstate ability to use Qemu on pre-SSE4.1 x86 hosts Message-ID: References: <20240612105525.8795-1-amonakov@ispras.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 11 X-Spam_score: 1.1 X-Spam_bar: + X-Spam_report: (1.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.143, 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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=no 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, Jun 12, 2024 at 01:21:26PM +0100, Daniel P. Berrangé wrote: > On Wed, Jun 12, 2024 at 01:51:31PM +0200, Paolo Bonzini wrote: > > On Wed, Jun 12, 2024 at 1:38 PM Daniel P. Berrangé wrote: > > > This isn't anything to do with the distro installer. The use case is that > > > the distro wants all its software to be able to run on the x86_64 baseline > > > it has chosen to build with. > > > > Sure, and they can patch the packages if their wish is not shared by > > upstream. Alternatively they can live with the fact that not all users > > will be able to use all packages, which is probably already the case. > > Yep, there's almost certainly scientific packages that have done > optimizations in their builds. QEMU is slightly more special > though because it is classed as a "critical path" package for > the distro. Even the QEMU linux-user pieces are now critical path, > since they're leveraged by docker & podman for running foreign arch > containers. > > > Or drop QEMU, I guess. Has FeSCO ever expressed how strict they are > > and which of the three options they'd pick? > > I don't know - i'm going to raise this question to find out if > there's any guidance. I learnt that FESCo approved a surprisingly loose rule saying "Libraries packaged in Fedora may require ISA extensions, however any packaged application must not crash on any officially supported architecture, either by providing a generic fallback implementation OR by cleanly exiting when the requisite hardware support is unavailable." This might suggest we could put a runtime feature check in main(), print a warning and then exit(1), however, QEMU has alot of code that is triggered from ELF constructors. If we're building the entire of QEMU codebase with extra features enabled, I worry that the constructors could potentially cause a illegal instruction crash before main() runs ? 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 :|