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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 1117AC43613 for ; Mon, 24 Jun 2019 08:39:28 +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 9C54F2089F for ; Mon, 24 Jun 2019 08:39:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9C54F2089F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:48798 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hfKVa-0004zL-Di for qemu-devel@archiver.kernel.org; Mon, 24 Jun 2019 04:39:26 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:41241) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hfKTx-0004Ex-63 for qemu-devel@nongnu.org; Mon, 24 Jun 2019 04:37:46 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hfKTu-0004Q8-4a for qemu-devel@nongnu.org; Mon, 24 Jun 2019 04:37:44 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48268) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hfKTk-00045H-4b; Mon, 24 Jun 2019 04:37:32 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 74009A7DD; Mon, 24 Jun 2019 08:37:30 +0000 (UTC) Received: from kinshicho (unknown [10.43.2.73]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 66EB45D721; Mon, 24 Jun 2019 08:37:26 +0000 (UTC) Message-ID: <7745c47186278c1b7f1781c9173ef0e2e8a55910.camel@redhat.com> From: Andrea Bolognani To: Peter Maydell , Cleber Rosa Date: Mon, 24 Jun 2019 10:37:24 +0200 In-Reply-To: References: <20190620222314.2670-1-wainersm@redhat.com> <20190621190421.GA679@localhost.localdomain> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.32.3 (3.32.3-1.fc30) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Mon, 24 Jun 2019 08:37:30 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [Qemu-arm] [RFC v2 PATCH] hw/arm/virt: makes virt a default machine type 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: , Cc: qemu-arm , QEMU Developers , Wainer dos Santos Moschetta Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Sat, 2019-06-22 at 16:58 +0100, Peter Maydell wrote: > On Fri, 21 Jun 2019 at 20:04, Cleber Rosa wrote: > > You can consider me biased (I do consider myself), but trying to wear > > the hat of a user first interacting with QEMU, I would expect a (any) > > reasonably capable environment that can represent the given target. > > That will probably be a different environment than the one I may need, > > and I think that's fine. > > I'm really not sure what you're trying to suggest here; maybe > you could clarify? If you specify a target (ie a machine type), > you get that machine type. If you don't specify a target, then > we can't really guess what you were hoping to run and > magically pick something that works. > > The main problem here is that users expect "all the world is a PC" > type behaviour, ie they can just provide qemu-system-arm or > qemu-system-aarch64 with no command line arguments except > a guest kernel (which is half the time something they found under > a rock or extracted from some firmware image) or a guest CDROM > image and have it boot, because that generally works for x86. It > doesn't and can't work for Arm, because of the much greater > diversity of machine types and the way that kernels are often > only compiled to work on a specific subset of machines. > Making the user specify a machine type means they do at least > get prompted that the world is more complicated than they > think it is and there are decisions that have to be made. > > In any case even if we did default to "virt" the user still > has to specify a CPU type, may well also want to provide > a GIC version (gicv3 being better than the default v2), > likely more RAM than the very small default, they need to provide > all the virtio devices, and so on and so on. So giving > them one option they no longer need to specify doesn't > really make it any easier IMHO. Additional note on GIC: most server-grade machines you can buy today do *not* support GICv2, so you will need to opt-in to GICv3 if you want your guest to even start. More generally, as someone who has worked on supporting non-x86 guests in libvirt for the past few years, I can tell you from experience that you're always going to need some arch-specific logic to deal with the small (and not so small :) differences in behavior between QEMU targets: as Peter correctly says, machine type is just a single example among many. -- Andrea Bolognani / Red Hat / Virtualization