From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36303) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XrNl5-0006p0-0k for qemu-devel@nongnu.org; Thu, 20 Nov 2014 04:10:40 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XrNkz-00014W-VY for qemu-devel@nongnu.org; Thu, 20 Nov 2014 04:10:34 -0500 Received: from mx1.redhat.com ([209.132.183.28]:40557) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XrNkz-00014C-N1 for qemu-devel@nongnu.org; Thu, 20 Nov 2014 04:10:29 -0500 Date: Thu, 20 Nov 2014 11:10:20 +0200 From: "Michael S. Tsirkin" Message-ID: <20141120091020.GA4050@redhat.com> References: <1416201070-11448-1-git-send-email-zhang.zhanghailiang@huawei.com> <1416201070-11448-2-git-send-email-zhang.zhanghailiang@huawei.com> <20141119103246.GE26395@redhat.com> <20141119101336.5893db6c@redhat.com> <546CBCB3.9040606@redhat.com> <20141119160628.GF28563@redhat.com> <546CC5E7.3010908@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <546CC5E7.3010908@redhat.com> Subject: Re: [Qemu-devel] [PATCH v2 1/3] pc-dimm: add a function to calculate VM's current RAM size List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: qemu-devel@nongnu.org, imammedo@redhat.com, peter.huangpeng@huawei.com, zhanghailiang , Luiz Capitulino On Wed, Nov 19, 2014 at 09:31:35AM -0700, Eric Blake wrote: > On 11/19/2014 09:06 AM, Michael S. Tsirkin wrote: > > >>>> This affects QMP right? > >>> > >>> I think later patches will tell how. CC'ing Eric. > >> > >> As far as I can tell, this is just correcting a reporting issue; the > >> existing QMP commands/events for tracking balloon size will now properly > >> account for hotplugged memory. > >> > >> What I don't know is if this change in semantics will affect any users. > >> Libvirt is not yet supporting memory hotplug, so ideally, fixing this > >> bug before libvirt uses memory hotplug means libvirt will never have to > >> worry about qemu versions that do incorrect reporting. > >> > >> The alternative is to declare that the existing QMP commands cannot > >> change in semantics for the existing members that it reports, and must > >> instead report additional dictionary members describing the amount of > >> hot-plugged memory, and then require that the client add the numbers > >> together itself. That sounds mean to the client, so I'm hoping we don't > >> have to go there. > > > > > > IOW you ack this patch for 2.2? > > > > Is memory hotplug one of the new features in 2.2? If so, then yes, we > should get its semantics right from the start (this is a bug fix to > avoid a release with broken semantics). On the other hand, if hotplug > existed in 2.1, then we already have a release with odd semantics, so > delaying this fix until 2.3 and leaving 2.2 with the same odd semantics > would not hurt, and it then becomes a judgment call of whether we are > rushing in a possibly incomplete solution by trying to get this into > 2.2. (Sorry I haven't been following the history of memory hotplug closer) AFAIK it's there since 2.0. > > -- > Eric Blake eblake redhat com +1-919-301-3266 > Libvirt virtualization library http://libvirt.org >