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 849E4C433E0 for ; Wed, 27 Jan 2021 15:11:13 +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 10A3D2075A for ; Wed, 27 Jan 2021 15:11:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 10A3D2075A 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]:33054 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l4mTQ-0008K3-2U for qemu-devel@archiver.kernel.org; Wed, 27 Jan 2021 10:11:12 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:33236) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l4mSL-0007cQ-8h for qemu-devel@nongnu.org; Wed, 27 Jan 2021 10:10:05 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:26992) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l4mSI-0002tK-Cp for qemu-devel@nongnu.org; Wed, 27 Jan 2021 10:10:05 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1611760201; 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=JAFFCRSdYd81FxjDSiKxz2ZYfCbZhyvwIv7ohY22JTY=; b=Rc5dYl2ZO/VJKX/XC3lA77DHIxX2oypwBAwG6Rnbnjy7sZlXCnynyZ9gVOIMoPFQ71FyZm SqwEpXFBuvyqIzSZLRILeyQtUjplGkY7xP06yAt9O2pt3l8ddJrU5NSPc6bA7RsY/Oo1Zi Rx7LvkpJZpuAZcYR+WELhEN22K/nTkk= 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-233-8G4cTKvlNzWSaqCzu6x4ig-1; Wed, 27 Jan 2021 10:09:56 -0500 X-MC-Unique: 8G4cTKvlNzWSaqCzu6x4ig-1 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 mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8DB3418C89FE; Wed, 27 Jan 2021 15:09:55 +0000 (UTC) Received: from redhat.com (ovpn-115-120.ams2.redhat.com [10.36.115.120]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 191015D6A1; Wed, 27 Jan 2021 15:09:52 +0000 (UTC) Date: Wed, 27 Jan 2021 15:09:50 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Michal Privoznik Subject: Re: [PATCH v3] machine: add missing doc for memory-backend option Message-ID: <20210127150950.GO3653144@redhat.com> References: <20210121161504.1007247-1-imammedo@redhat.com> <20210127104511.GF3653144@redhat.com> <20210127105436.GG3653144@redhat.com> <756c025a-3811-4a36-98a2-3a02bd756523@redhat.com> MIME-Version: 1.0 In-Reply-To: <756c025a-3811-4a36-98a2-3a02bd756523@redhat.com> User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 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: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.308, 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_H3=0.001, RCVD_IN_MSPIKE_WL=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: Igor Mammedov , pkrempa@redhat.com, qemu-devel@nongnu.org, pbonzini@redhat.com, peter.maydell@linaro.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Jan 27, 2021 at 03:24:26PM +0100, Michal Privoznik wrote: > On 1/27/21 11:54 AM, Daniel P. Berrangé wrote: > > On Wed, Jan 27, 2021 at 10:45:11AM +0000, Daniel P. Berrangé wrote: > > > On Thu, Jan 21, 2021 at 11:15:04AM -0500, Igor Mammedov wrote: > > > > > > > > How does a mgmt app know which machine types need to use this > > > option ? The machine type names are opaque strings, and apps > > > must not attempt to parse or interpret the version number > > > inside the machine type name, as they can be changed by > > > distros. IOW, saying to use it for machine types 4.0 and > > > older isn't a valid usage strategy IMHO. > > > > Looking at the libvirt patch, we do indeed use his property > > unconditionally for all machine types, precisely because parsing > > version numbers from the machine type is not allowed. > > > > https://www.redhat.com/archives/libvir-list/2021-January/msg00633.html > > > > So this doc is telling apps to do something that isn't viable > > The other approach that I was suggesting was, that QEMU stops reporting > 'default-ram-id' for affected machine types. The way the switch from '-m > XMB' to memory-backend-* was implemented in libvirt is that if libvirt sees > 'default-ram-id' attribute for given machine type it uses memory-backend-* > otherwise it falls back to -m. > > Since we know which machine types are "broken", we can stop reporting the > attribute and thus stop tickling this bug. I agree that it puts more burden > on distro maintainers to backport the change, but I think it's acceptable > risk. IIUC That's only a burden for distros if they're creating their own machine types, in which case they've already decided the burden is a net win. 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 :|