From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49573) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XWLuU-0000qz-UY for qemu-devel@nongnu.org; Tue, 23 Sep 2014 04:57:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XWLuO-00006j-RA for qemu-devel@nongnu.org; Tue, 23 Sep 2014 04:57:22 -0400 Received: from [59.151.112.132] (port=46676 helo=heian.cn.fujitsu.com) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XWLuO-000067-DG for qemu-devel@nongnu.org; Tue, 23 Sep 2014 04:57:16 -0400 Message-ID: <54213648.5070608@cn.fujitsu.com> Date: Tue, 23 Sep 2014 16:58:48 +0800 From: Tang Chen MIME-Version: 1.0 References: <1410863956-11056-1-git-send-email-zhang.zhanghailiang@huawei.com> <1410863956-11056-2-git-send-email-zhang.zhanghailiang@huawei.com> <20140917083220.GA17032@G08FNSTD100614.fnst.cn.fujitsu.com> <20140919142642.7d7fbd3d@nial.usersys.redhat.com> <541FE5D0.9050705@cn.fujitsu.com> <20140923104047.4ef196f9@nial.usersys.redhat.com> In-Reply-To: <20140923104047.4ef196f9@nial.usersys.redhat.com> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 1/2] pc-dimm: No numa option shouldn't break hotplug memory feature List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Igor Mammedov Cc: Peter , zhanghailiang , mst@redhat.com, Hu Tao , luonengjun@huawei.com, qemu-devel@nongnu.org, peter.huangpeng@huawei.com, pbonzini@redhat.com, gaowanlong@cn.fujitsu.com On 09/23/2014 04:40 PM, Igor Mammedov wrote: > ...... > It's fine to use SRAT for these purposes on baremetal NUMA systems since > due to used chipset constrains it's possible statically allocate ranges > for every possible DIMM socket. > However SRAT(which is optional table BTW) entries are not mandatory > and override-able by ACPI Device's _PXM/_CRS methods replacing needs > for SRAT entries and QEMU uses this fact by supplying these methods. > QEMU adds FAKE SRAT entry only to workaround Windows limitation, > and for nothing else. > > I think Linux does not violate ACPI spec and behaves as expected, moreover > it's more correct than Windows since memory hotplug will work on non NUMA > machines as well. > > Hence I think this patch is correct and allows memory hotplug in absence > of NUMA configuration. It also would allow to use pc-dimm as replacement > for initial memory for non-NUMA configs (which is on my TODO list) > > As for the Windows, QEMU has no idea what OS it would be running, > I see 2 ways to solve issue: > 1. user should know that memory hotplug on Windows requires NUMA machine > and specify "-numa ..." option for this case. > (I've discussed this with libvirt folks and was promised that > if user enables memory hotplug, libvirt would provide "-numa" option > to workaround Windows issue) > > 2. QEMU could unconditionally create single NUMA if memory hotplug is > enabled. (but that should be enable only for 2.2 or late machines > to avoid migration issues) > I prefer 2. I'll try to send patches for it if Zhang is also OK with it. Thanks. :)