Re: [Qemu-devel] NVDIMM live migration broken?

[Haozhong Zhang]

On 06/23/17 10:55 +0100, Stefan Hajnoczi wrote:
> On Fri, Jun 23, 2017 at 08:13:13AM +0800, address@hidden wrote:
> > On 06/22/17 15:08 +0100, Stefan Hajnoczi wrote:
> > > I tried live migrating a guest with NVDIMM on qemu.git/master (edf8bc984):
> > > 
> > >   $ qemu -M accel=kvm,nvdimm=on -m 1G,slots=4,maxmem=8G -cpu host \
> > >          -object 
> > > memory-backend-file,id=mem1,share=on,mem-path=nvdimm.dat,size=1G \
> > >    -device nvdimm,id=nvdimm1,memdev=mem1 \
> > >    -drive if=virtio,file=test.img,format=raw
> > > 
> > >   $ qemu -M accel=kvm,nvdimm=on -m 1G,slots=4,maxmem=8G -cpu host \
> > >          -object 
> > > memory-backend-file,id=mem1,share=on,mem-path=nvdimm.dat,size=1G \
> > >    -device nvdimm,id=nvdimm1,memdev=mem1 \
> > >    -drive if=virtio,file=test.img,format=raw \
> > >    -incoming tcp::1234
> > > 
> > >   (qemu) migrate tcp:127.0.0.1:1234
> > > 
> > > The guest kernel panics or hangs every time on the destination.  It
> > > happens as long as the nvdimm device is present - I didn't even mount it
> > > inside the guest.
> > > 
> > > Is migration expected to work?
> > 
> > Yes, I tested on QEMU 2.8.0 several months ago and it worked. I'll
> > have a look at this issue.
> 
> Great, thanks!
> 
> David Gilbert suggested the following on IRC, it sounds like a good
> starting point for debugging:
> 
> Launch the destination QEMU with -S (vcpus will be paused) and after
> migration has completed, compare the NVDIMM contents on source and
> destination.
> 

Which host and guest kernel are you testing? Is any workload running
in guest when migration?

I just tested QEMU commit edf8bc984 with host/guest kernel 4.8.0, and
could not reproduce the issue.

Haozhong