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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 2438BC63793 for ; Thu, 22 Jul 2021 13:52:14 +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 D40C96109D for ; Thu, 22 Jul 2021 13:52:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D40C96109D 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]:38748 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1m6Z7V-0006hn-2D for qemu-devel@archiver.kernel.org; Thu, 22 Jul 2021 09:52:13 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:40600) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1m6Z4U-0002EA-5y for qemu-devel@nongnu.org; Thu, 22 Jul 2021 09:49:06 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:46468) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1m6Z4P-00064y-Dn for qemu-devel@nongnu.org; Thu, 22 Jul 2021 09:49:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1626961737; 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=9nbyfsZL9jHrsLqTBbLwf028h6vjDeU1TSdRDuTJiDY=; b=IReLS3P0cneRCLQD++nA3AyxQ78S7ZdzMNJYsJBto8o6Xp4Kq4gjeqX3cnd/k9tP9B+NiH ifpLTHqF1XAxbg0ffkIZ7upM2+vJ2e6ZtKmeyTULdmu8NOSUA0OoJeVedkTRYEp+u4aTDF Tu2bes4cEWj8eOEwfxwJ/L+H771Ddnc= 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-345-D1mQt_B1OrCl9WfWNsOTXA-1; Thu, 22 Jul 2021 09:48:56 -0400 X-MC-Unique: D1mQt_B1OrCl9WfWNsOTXA-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 10E2F1812FC5; Thu, 22 Jul 2021 13:48:55 +0000 (UTC) Received: from localhost (ovpn-112-132.ams2.redhat.com [10.36.112.132]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 507285D6A8; Thu, 22 Jul 2021 13:48:54 +0000 (UTC) From: Cornelia Huck To: Andrew Jones Subject: Re: [PATCH for-6.1 0/1] machine: Disallow specifying topology parameters as zero In-Reply-To: <20210722133759.db2kjcoucf6rsz4o@gator> Organization: Red Hat GmbH References: <20210722021512.2600-1-wangyanan55@huawei.com> <87y29y7uon.fsf@redhat.com> <20210722133759.db2kjcoucf6rsz4o@gator> User-Agent: Notmuch/0.32.1 (https://notmuchmail.org) Date: Thu, 22 Jul 2021 15:48:52 +0200 Message-ID: <87eebq792z.fsf@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=cohuck@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=216.205.24.124; envelope-from=cohuck@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 5.0 requ) DKIMWL_WL_HIGH=-1.472, 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_H4=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: , Cc: Peter Maydell , =?utf-8?Q?Daniel_P_=2E_Berrang=C3=A9?= , Eduardo Habkost , Pierre Morel , Pankaj Gupta , qemu-devel@nongnu.org, Markus Armbruster , Yanan Wang , wanghaibin.wang@huawei.com, yuzenghui@huawei.com, Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Jul 22 2021, Andrew Jones wrote: > On Thu, Jul 22, 2021 at 08:02:16AM +0200, Cornelia Huck wrote: >> On Thu, Jul 22 2021, Yanan Wang wrote: >> >> > In the SMP configuration, we should either specify a topology >> > parameter with a reasonable value (equal to or greater than 1) >> > or just leave it omitted and QEMU will calculate its value. >> > Configurations which explicitly specify the topology parameters >> > as zero like "sockets=0" are meaningless, so disallow them. >> > >> > However; the commit 1e63fe685804d >> > (machine: pass QAPI struct to mc->smp_parse) has documented that >> > '0' has the same semantics as omitting a parameter in the qapi >> > comment for SMPConfiguration. So this patch fixes the doc and >> > also adds the corresponding sanity check in the smp parsers. >> >> Are we expecting any real users to have used that 'parameter=0' >> behaviour? I expect that libvirt and other management software already >> did the right thing; unfortunately, sometimes weird configuration lines >> tend to persist in search results. > > I understand this concern. I think the only documentation we had prior to > commit 1e63fe685804 was > > DEF("smp", HAS_ARG, QEMU_OPTION_smp, > "-smp [cpus=]n[,maxcpus=cpus][,cores=cores][,threads=threads][,dies=dies][,sockets=sockets]\n" > " set the number of CPUs to 'n' [default=1]\n" > " maxcpus= maximum number of total cpus, including\n" > " offline CPUs for hotplug, etc\n" > " cores= number of CPU cores on one socket (for PC, it's on one die)\n" > " threads= number of threads on one CPU core\n" > " dies= number of CPU dies on one socket (for PC only)\n" > " sockets= number of discrete sockets in the system\n", > QEMU_ARCH_ALL) > SRST > ``-smp [cpus=]n[,cores=cores][,threads=threads][,dies=dies][,sockets=sockets][,maxcpus=maxcpus]`` > Simulate an SMP system with n CPUs. On the PC target, up to 255 CPUs > are supported. On Sparc32 target, Linux limits the number of usable > CPUs to 4. For the PC target, the number of cores per die, the > number of threads per cores, the number of dies per packages and the > total number of sockets can be specified. Missing values will be > computed. If any on the three values is given, the total number of > CPUs n can be omitted. maxcpus specifies the maximum number of > hotpluggable CPUs. > ERST > > This doesn't mention zero inputs and even implies non-zero inputs. Yes, hopefully that kept people away from using 0 magic, unless they read the code. > > I'm not sure if we need to worry about the odd command line that used zero > for some parameters. What do you think? I did a cursory search for bad examples, and nothing popped up. So this should be reasonably painless.