Re: [Xen-devel] [RFC Design Doc] Add vNVDIMM support for Xen

["Zhang, Haozhong" <haozhong.zhang@xxxxxxxxx>]

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

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