From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Zhang, Haozhong" Subject: Re: [RFC Design Doc] Add vNVDIMM support for Xen Date: Tue, 2 Feb 2016 15:53:16 +0800 Message-ID: <20160202075316.GJ6293@hz-desktop.sh.intel.com> References: <20160201054414.GA25211@hz-desktop.sh.intel.com> <20160202073901.GI6293@hz-desktop.sh.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: "Tian, Kevin" Cc: Juergen Gross , Wei Liu , Ian Campbell , George Dunlap , Andrew Cooper , Stefano Stabellini , Ian Jackson , "xen-devel@lists.xen.org" , Jan Beulich , "Nakajima, Jun" , Xiao Guangrong , Keir Fraser List-Id: xen-devel@lists.xenproject.org On 02/02/16 15:48, Tian, Kevin wrote: > > From: Zhang, Haozhong > > Sent: Tuesday, February 02, 2016 3:39 PM > > > > > btw, how is persistency guaranteed in KVM/QEMU, cross guest > > > power off/on? I guess since Qemu process is killed the allocated pmem > > > will be freed so you may switch to file-backed method to keep > > > persistency (however copy would take time for large pmem trunk). Or > > > will you find some way to keep pmem managed separated from qemu > > > qemu life-cycle (then pmem is not efficiently reused)? > > > > > > > It all depends on guests themselves. clwb/clflushopt/pcommit > > instructions are exposed to guest that are used by guests to make > > writes to pmem persistent. > > > > I meant from guest p.o.v, a range of pmem should be persistent > cross VM power on/off, i.e. the content needs to be maintained > somewhere so guest can get it at next power on... > > Thanks > Kevin It's just like what we do for guest disk: as long as we always assign the same host pmem device or the same files on file systems on a host pmem device to the guest, the guest can find its last data on pmem. Haozhong