From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45975) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1f8RaV-0005UD-7f for qemu-devel@nongnu.org; Tue, 17 Apr 2018 10:28:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1f8RaS-0006mG-G0 for qemu-devel@nongnu.org; Tue, 17 Apr 2018 10:28:03 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52066) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1f8RaS-0006ln-AY for qemu-devel@nongnu.org; Tue, 17 Apr 2018 10:28:00 -0400 Date: Tue, 17 Apr 2018 11:27:39 -0300 From: Eduardo Habkost Message-ID: <20180417142739.GV29865@localhost.localdomain> References: <1520860275-101576-1-git-send-email-imammedo@redhat.com> <87zi21apkh.fsf@dusky.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87zi21apkh.fsf@dusky.pond.sub.org> Subject: Re: [Qemu-devel] [PATCH v4 0/9] enable numa configuration before machine_init() from QMP List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus Armbruster Cc: Igor Mammedov , qemu-devel@nongnu.org, peter.maydell@linaro.org, pkrempa@redhat.com, cohuck@redhat.com, pbonzini@redhat.com, david@gibson.dropbear.id.au On Tue, Apr 17, 2018 at 04:13:34PM +0200, Markus Armbruster wrote: > Igor Mammedov writes: > > [...] > > Series allows to configure NUMA mapping at runtime using QMP > > interface. For that to happen it introduces a new '-preconfig' CLI option > > which allows to pause QEMU before machine_init() is run and > > adds new set-numa-node QMP command which in conjunction with > > query-hotpluggable-cpus allows to configure NUMA mapping for cpus. > > > > Later we can modify other commands to run early, for example device_add. > > I recall SPAPR had problem when libvirt started QEMU with -S and, while it's > > paused, added CPUs with device_add. Intent was to coldplug CPUs (but at that > > stage it's considered hotplug already), so SPAPR had to work around the issue. > > That instance is just stupidity / laziness, I think: we consider any > plug after machine creation a hot plug. Real machines remain cold until > you press the power button. Our virtual machines should remain cold > until they start running, i.e. with -S until the first "cont". > > I vaguely remember me asking this before, but your answer didn't make it > into this cover letter, which gives me a pretext to ask again instead of > looking it up in the archives: what exactly prevents us from keeping the > machine cold enough for numa configuration until the first "cont"? I also think this would be better, but it seems to be difficult in practice, see: http://mid.mail-archive.com/20180323210532.GD28161@localhost.localdomain -- Eduardo