Re: [libvirt] [PATCH 0/5] Introduce NVDIMM support

On Mon, Aug 1, 2016 at 4:10 PM, Michal Privoznik <mprivozn(a)redhat.com&gt; wrote: > NVDIMM was introduced to qemu in v2.6.0-rc0~248^2~25. So it's > been a while since then. > > It's not the next big thing, but it is very interesting feature > enabling higher performance as reading/writing to the module (and > subsequently to the file on the host) does not require a VMEXIT. > It can be used to access host files directly bypassing page cache > whilst doing so. > > > How to test the feature? > 1) you need PMEM enabled kernel: > CONFIG_LIBNVDIMM=y > CONFIG_BLK_DEV_PMEM=m > CONFIG_ACPI_NFIT=m > > 2) Create a file in the host: > truncate -s 512M /tmp/nvdimm > > 3) Add the following to the domain XML: > > <memory model='nvdimm' memAccess='shared'> > <source> > <path>/tmp/nvdimm</path> > </source> > <target> > <size unit='KiB'>523264</size> > <node>0</node> > </target> > </memory> The "nvdimm" device also has a label-size property. This determines the size of the Namespace Label area described in: http://pmem.io/documents/NVDIMM_Namespace_Spec.pdf By default no Namespace Label area is reserved in the file. If the user specifies label-size then the memory at the end of the file is used as the Namespace Label area. It is necessary to expose label-size so users can choose whether or not to have a Namespace Label area. I have CCed Guangrong Xiao who authored the QEMU patches.