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

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On 10/13/2015 12:36 AM, Dan Williams wrote:
On Sun, Oct 11, 2015 at 9:33 PM, Xiao Guangrong
<guangrong.xiao@xxxxxxxxxxxxxxx> wrote:


On 10/11/2015 05:17 AM, Dan Williams wrote:

On Sat, Oct 10, 2015 at 8:52 PM, Xiao Guangrong
<guangrong.xiao@xxxxxxxxxxxxxxx> 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.

This is Linux specific? As i did not see it has been documented in the
spec...


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.

Okay, thanks for your nice explanation, Dan!

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