From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52106) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XrHWt-0004NG-1t for qemu-devel@nongnu.org; Wed, 19 Nov 2014 21:31:37 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XrHWm-0004in-To for qemu-devel@nongnu.org; Wed, 19 Nov 2014 21:31:31 -0500 Received: from szxga02-in.huawei.com ([119.145.14.65]:17275) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XrHWm-0004hO-A8 for qemu-devel@nongnu.org; Wed, 19 Nov 2014 21:31:24 -0500 Message-ID: <546D5265.20803@huawei.com> Date: Thu, 20 Nov 2014 10:31:01 +0800 From: zhanghailiang MIME-Version: 1.0 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> In-Reply-To: <546CC5E7.3010908@redhat.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit 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 , "Michael S. Tsirkin" Cc: imammedo@redhat.com, peter.huangpeng@huawei.com, qemu-devel@nongnu.org, borntraeger@de.ibm.com, Luiz Capitulino On 2014/11/20 0:31, 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 No, after searching this feature in ChangeLogs, i found pc-dimm memory hotplug was supported since 2.1. It only supports for x86 target. And one more thing, i found in 2.2's Changelog it begin to support memory hotplug for s390 target, I'm not sure whether this problem also exists for s390. > 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) > >