Re: [Qemu-discuss] [Qemu-devel] Devdax backend for vnvdimm not working

[Luyao Zhong]

On 2019/1/16 下午1:49, Yi Zhang wrote:
> On 2019-01-15 at 22:51:09 +0000, Kamal Kakri via Qemu-devel wrote:
> >   My devdax device is 2MB aligned so I dont think this is alignment related.# 
> > ndctl list -X -n namespace0.0
> > [
> >    {
> >      "dev":"namespace0.0",
> >      "mode":"devdax",
> >      "map":"dev",
> >      "size":16909336576,
> >      "uuid":"e5265c0a-d902-41ce-b1d1-87a78c358aa4",
> >      "daxregion":{
> >        "id":0,
> >        "size":16909336576,
> >        "align":2097152,  ------------------------->
> >        "devices":[
> >          {
> >            "chardev":"dax0.0",
> >            "size":16909336576
> >          }
> >        ]
> >      }
> >    }
> > ]
> >
> >
> > I even tried to create vnvdimm of exact same size as my devdax namespace, 
> > thinking that it would not need to ftruncate in that case but I still get the 
> > same error:
> > # virsh start fox22vm
> > start: domain(optdata): fox22vm
> > start: found option <domain>: fox22vm
> > start: <domain> trying as domain NAME
> > error: Failed to start domain fox22vm
> > error: internal error: qemu unexpectedly closed the monitor: ftruncate: Invalid 
> > argument
> > 2019-01-15T21:58:52.647221Z qemu-kvm: -object 
> > memory-backend-file,id=memnvdimm0,prealloc=yes,mem-path=/dev/dax0.0,share=yes,size=16909336576:
> >  unable to map backing store for guest RAM: Invalid argument
> >
> >
> > Has anyone ever got devdax backed vnvdimm configured and working?
> > If yes then pls let me know what libvirt/qemu/kernel version you have used to 
> > get it working.
> >
> > Thanks.
> >      On Tuesday, January 15, 2019, 3:13:27 PM EST, Kamal Kakri <address@hidden> 
> > wrote:
> >   
> >   Hi,
> >
> > I have a namespace (backed by real nvdimm h/w) configured in devdax mode:
> > # ndctl list -N -n namespace0.0
> > [
> >    {
> >      "dev":"namespace0.0",
> >      "mode":"devdax",
> >      "map":"dev",
> >      "size":16909336576,
> >      "uuid":"e5265c0a-d902-41ce-b1d1-87a78c358aa4",
> >      "chardev":"dax0.0"
> >    }
> > ]
> >
> >
> > When I try to configure my vm using "virsh" with something like this:
> >      <memory model='nvdimm' access='shared'>
> >        <source>
> >          <path>/dev/dax0.0</path>
> >          <align unit='KiB'>2048</align>
> this should be alignsize, Add Luyao.
This option is supported in Libvirt master now, will be in release 
5.0.0. I noticed that you use v4.5.0, it doesn't support 'alignsize' and 
'pmem'.
> >          <pmem/>
> >        </source>
> >        <target>
> >          <size unit='KiB'>2097152</size>
> >          <node>0</node>
> >        </target>
> >        <alias name='nvdimm0'/>
> >        <address type='dimm' slot='0'/>
> >      </memory>
> >
> >
> > I get an error while starting my vm:
> > # virsh start fox22vm
> > start: domain(optdata): fox22vm
> > start: found option <domain>: fox22vm
> > start: <domain> trying as domain NAME
> > error: Failed to start domain fox22vm
> > error: internal error: qemu unexpectedly closed the monitor: ftruncate: Invalid 
> > argument
> > 2019-01-15T18:00:36.587467Z qemu-kvm: -object 
> > memory-backend-file,id=memnvdimm0,prealloc=yes,mem-path=/dev/dax0.0,share=yes,size=2147483648:
> >  unable to map backing store for guest RAM: Invalid argument
> >
> > I have tried to add "align unit" to my virsh xml but it does not seem to pass 
> > it onto qemu (as much as I can see from the qemu cmd line in the logs at 
> > /var/log/libvirt/qemu)
> >
> >
> > Can anyone pls hint as to what possibly could be the issue ? Is this alignment 
> > related or something else ?
> >
> > Here are my versions:
> > # virsh --version
> > 4.5.0
> > address@hidden libexec]# /usr/libexec/qemu-kvm --version
> > QEMU emulator version 2.12.0 (qemu-kvm-rhev-2.12.0-18.el7_6.1)
> > Copyright (c) 2003-2017 Fabrice Bellard and the QEMU Project developers
> > # uname -a
> > Linux fox22hv 4.19.0-1.el7.elrepo.x86_64 #1 SMP Mon Oct 22 10:40:32 EDT 2018 
> > x86_64 x86_64 x86_64 GNU/Linux
> >
> >
> >
> >
> >