Re: qemu-emulated nfit devices disappeared

[Dan Williams <dan.j.williams@intel.com>]

On Thu, Nov 4, 2021 at 9:04 AM Christoph Hellwig <hch@infradead.org> wrote:
>
> On Thu, Nov 04, 2021 at 09:00:01AM -0700, Dan Williams wrote:
> > > Any idea what might be missing in the attached config?  This seems to
> > > be independent of the tested kernel version (5.14, 5.15, master).
> >
> > Can you share your qemu command line
>
> qemu-system-x86_64 -enable-kvm \
>         -machine pc,nvdimm=on \
>         -m 4096,slots=8,maxmem=32G \
>         -smp 4 \
>         -kernel arch/x86/boot/bzImage \
>         -append "root=/dev/vda1 console=ttyS0,115200n8" \
>         -nographic \
>         -drive if=virtio,file=/home/hch/images/jessie.img,cache=none \
>         -object memory-backend-file,id=mem0,mem-path=/home/hch/images/test.img,share=yes,prealloc=no,align=128M,size=10G \
>         -device nvdimm,id=nvdimm0,memdev=mem0,slot=0,label-size=2M \
>         -object memory-backend-file,id=mem1,mem-path=/home/hch/images/scratch.img,share=yes,prealloc=no,align=128M,size=10G \
>         -device nvdimm,id=nvdimm1,memdev=mem1,slot=1,label-size=2M \
>
>
> > and the output of:
> >
> > ndctl list -vvv
>
>
> [
>   {
>     "provider":"ACPI.NFIT",
>     "dev":"ndbus0",
>     "dimms":[
>       {
>         "dev":"nmem1",
>         "id":"8680-57341200",
>         "handle":2,
>         "phys_id":0
>       },
>       {
>         "dev":"nmem0",
>         "id":"8680-56341200",
>         "handle":1,
>         "phys_id":0
>       }
>     ],
>     "regions":[
>       {
>         "dev":"region1",
>         "size":10603200512,
>         "available_size":10603200512,

Hmm, so the driver has 2 modes "labeled" and "label-less", in the
labeled mode it waits for an explicit:

    ndctl create-namespace

...to provision region capacity into a namespace. In label-less mode
it just assumes that the boundaries of the region are the boundaries
of the namespace. In this case it looks like the driver found a label
index block with no namespaces defined so it's waiting for one to be
created. Are you saying that the only thing you changed from a working
config with defined namespace to this one was a kernel change? I.e.
the content of those memory-backend files has not changed?


>         "max_available_extent":10603200512,
>         "type":"pmem",
>         "iset_id":52512795602891997,
>         "mappings":[
>           {
>             "dimm":"nmem1",
>             "offset":0,
>             "length":10603200512,
>             "position":0
>           }
>         ],
>         "persistence_domain":"unknown",
>         "namespaces":[
>           {
>             "dev":"namespace1.0",
>             "mode":"raw",
>             "size":0,
>             "uuid":"00000000-0000-0000-0000-000000000000",
>             "sector_size":512,
>             "state":"disabled"
>           }
>         ]
>       },
>       {
>         "dev":"region0",
>         "size":10603200512,
>         "available_size":10603200512,
>         "max_available_extent":10603200512,
>         "type":"pmem",
>         "iset_id":52512752653219036,
>         "mappings":[
>           {
>             "dimm":"nmem0",
>             "offset":0,
>             "length":10603200512,
>             "position":0
>           }
>         ],
>         "persistence_domain":"unknown",
>         "namespaces":[
>           {
>             "dev":"namespace0.0",
>             "mode":"raw",
>             "size":0,
>             "uuid":"00000000-0000-0000-0000-000000000000",
>             "sector_size":512,
>             "state":"disabled"
>           }
>         ]
>       }
>     ]
>   }
> ]