Re: [Qemu-devel] [PATCH] docs/nvdimm: add example on persistent backend setup

[Pankaj Gupta]

> 
> Persistent backend setup requires some knowledge about nvdimm and ndctl
> tool. Some users report they may struggle to gather these knowledge and
> have difficulty to setup it properly.
> 
> Here we provide two examples for persistent backend and gives the link
> to ndctl. By doing so, user could try it directly and do more
> investigation on persistent backend setup with ndctl.
> 
> Signed-off-by: Wei Yang <address@hidden>
> ---
>  docs/nvdimm.txt | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/docs/nvdimm.txt b/docs/nvdimm.txt
> index b531cacd35..baba7a940d 100644
> --- a/docs/nvdimm.txt
> +++ b/docs/nvdimm.txt
> @@ -171,6 +171,32 @@ guest software that this vNVDIMM device contains a
> region that cannot
>  accept persistent writes. In result, for example, the guest Linux
>  NVDIMM driver, marks such vNVDIMM device as read-only.
>  
> +Backend File Setup Example
> +..........................
> +
> +Here is two examples for how to setup these persistent backend on
> +linux, which leverages the tool ndctl [3].
> +
> +It is easy to setup DAX device backend file.
> +
> +A. DAX device
> +
> +    ndctl create-namespace -f -e namespace0.0 -m devdax
> +
> +The /dev/dax0.0 could be used directly in "mem-path" option.
> +
> +For DAX file, it is more than creating the proper namespace. The
> +block device should be partitioned and mounted (with dax option).
> +
> +B. DAX file
> +
> +    ndctl create-namespace -f -e namespace0.0 -m fsdax
> +    (partition /dev/pmem0 with name pmem0p1)
> +    mount -o dax /dev/pmem0p1 /mnt
> +    (dd a file with proper size in /mnt)

This is not clear to me. why 'dd' file is required in /mnt?
You mean for creating a backend file?

> +
> +Then the new file in /mnt could be used in "mem-path" option.
> +
>  NVDIMM Persistence
>  ------------------
>  
> @@ -212,3 +238,5 @@ References
>      
> https://www.snia.org/sites/default/files/technical_work/final/NVMProgrammingModel_v1.2.pdf
>  [2] Persistent Memory Development Kit (PMDK), formerly known as NVML
>  project, home page:
>      http://pmem.io/pmdk/
> +[3] ndctl-create-namespace - provision or reconfigure a namespace
> +    http://pmem.io/ndctl/ndctl-create-namespace.html
> --

Looks good to me. Just a small comment above. 
Other than that: Reviewed-by: Pankaj Gupta <address@hidden>

> 2.17.1
> 
> 
>