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

[Wei Yang]

Hi, Stefan

Thanks for your comments :-)

On Mon, Jul 29, 2019 at 02:58:59PM +0100, Stefan Hajnoczi wrote:
>On Wed, Jul 24, 2019 at 03:03:07PM +0800, Wei Yang wrote:
>> 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 I use '-' because I want to say this is a sub-section of "Guest Data
Persistence".

Actually, I struggled a little to pick up a proper character. Do you think '-'
is the proper one?

>
>For consistency with the rest of the document please use '-' instead of
>'.'.
>
>> +
>> +Here is two examples for how to setup these persistent backend on
>> +linux, which leverages the tool ndctl [3].
>
>Small grammar tweaks:
>
>  Here are two examples showing how to set up persistent backends on
>  Linux using the tool ndctl [3].
>
>> +
>> +It is easy to setup DAX device backend file.
>
>Please move this into the "A. DAX device" section and use it as an
>introduction to explain what this section is about:
>
>  Use the following command to set up /dev/dax0.0 so that the entirety
>  of namespace0.0 can be exposed as an emulated NVDIMM to the guest:
>
>> +
>> +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).
>
>Please move this into "B. DAX file":
>
>  Individual files on a DAX host file system can be exposed as emulated
>  NVDIMMS.  First an fsdax block device is created, partitioned, and
>  then mounted with the "dax" mount 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)
>
>"dd a file" could be "create or copy a disk image file with qemu-img(1),
>cp(1), or dd(1) in /mnt".



-- 
Wei Yang
Help you, Help me