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From: Xiao Guangrong <guangrong.xiao@linux.intel.com>
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Date: Mon, 12 Oct 2015 12:33:26 +0800
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Subject: Re: [Qemu-devel] [PATCH v3 00/32] implement vNVDIMM
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To: Dan Williams <dan.j.williams@intel.com>
Cc: ehabkost@redhat.com, kvm@vger.kernel.org, "Michael S. Tsirkin" <mst@redhat.com>, Gleb Natapov <gleb@kernel.org>, mtosatti@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com, imammedo@redhat.com, Paolo Bonzini <pbonzini@redhat.com>, rth@twiddle.net



On 10/11/2015 05:17 AM, Dan Williams wrote:
> On Sat, Oct 10, 2015 at 8:52 PM, Xiao Guangrong
> <guangrong.xiao@linux.intel.com> 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...

> 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?