Re: [Qemu-devel] [PATCH v3 00/32] implement vNVDIMM

[Dan Williams]

On Sun, Oct 11, 2015 at 9:33 PM, Xiao Guangrong
<address@hidden> wrote:
>
>
> On 10/11/2015 05:17 AM, Dan Williams wrote:
>>
>> On Sat, Oct 10, 2015 at 8:52 PM, Xiao Guangrong
>> <address@hidden> wrote:
>> [..]
>>>
>>> ====== Test ======
>>> In host
>>> 1) create memory backed file, e.g # dd if=zero of=/tmp/nvdimm bs=1G
>>> count=10
>>> 2) append "-object memory-backend-file,share,id=mem1,
>>>     mem-path=/tmp/nvdimm -device nvdimm,memdev=mem1,reserve-label-data,
>>>     id=nv1" in QEMU command line
>>>
>>> In guest, download the latest upsteam kernel (4.2 merge window) and
>>> enable
>>> ACPI_NFIT, LIBNVDIMM and BLK_DEV_PMEM.
>>> 1) insmod drivers/nvdimm/libnvdimm.ko
>>> 2) insmod drivers/acpi/nfit.ko
>>> 3) insmod drivers/nvdimm/nd_btt.ko
>>> 4) insmod drivers/nvdimm/nd_pmem.ko
>>> You can see the whole nvdimm device used as a single namespace and
>>> /dev/pmem0
>>> appears. You can do whatever on /dev/pmem0 including DAX access.
>>>
>>> Currently Linux NVDIMM driver does not support namespace operation on
>>> this
>>> kind of PMEM, apply below changes to support dynamical namespace:
>>>
>>> @@ -798,7 +823,8 @@ static int acpi_nfit_register_dimms(struct
>>> acpi_nfit_desc *a
>>>                          continue;
>>>                  }
>>>
>>> -               if (nfit_mem->bdw && nfit_mem->memdev_pmem)
>>> +               //if (nfit_mem->bdw && nfit_mem->memdev_pmem)
>>> +               if (nfit_mem->memdev_pmem)
>>>                          flags |= NDD_ALIASING;
>>
>>
>> This is just for testing purposes, right?  I expect guests can
>
>
> It's used to validate NVDIMM _DSM method and static namespace following
> NVDIMM specs...

Static namespaces can be emitted without a label.  Linux needs this to
support existing "label-less" bare metal NVDIMMs.

>> sub-divide persistent memory capacity by partitioning the resulting
>> block device(s).
>
>
> I understand that it's a Linux design... Hmm, can the same expectation
> apply to PBLK?

BLK-mode is a bit different as those namespaces have both configurable
sector-size and an optional BTT.  It is possible to expect multiple
BLK namespaces per a given region with different settings.