Re: [Qemu-discuss] [Qemu-devel] Devdax backend for vnvdimm not working

[Wei Yang]

On Wed, Jan 16, 2019 at 10:18:05AM +0800, Yi Zhang wrote:
>On 2019-01-16 at 09:12:33 +0800, Wei Yang wrote:
>> On Tue, Jan 15, 2019 at 08:13:27PM +0000, Kamal Kakri via Qemu-devel wrote:
>> >Hi,
>> >
>> >I have a namespace (backed by real nvdimm h/w) configured in devdax mode:
>> ># ndctl list -N -n namespace0.0
>> >[
>> >  {
>> >    "dev":"namespace0.0",
>> >    "mode":"devdax",
>> >    "map":"dev",
>> >    "size":16909336576,
>> >    "uuid":"e5265c0a-d902-41ce-b1d1-87a78c358aa4",
>> >    "chardev":"dax0.0"
>> >  }
>> >]
>> >
>> 
>> Above is your host configuration, right?
>> 
>> >
>> >When I try to configure my vm using "virsh" with something like this:
>> >    <memory model='nvdimm' access='shared'>
>> >      <source>
>> >        <path>/dev/dax0.0</path>
>> >        <align unit='KiB'>2048</align>
>so that will apply the align=2048K for memory-backend-file?
>> >        <pmem/>
>> >      </source>
>> >      <target>
>> >        <size unit='KiB'>2097152</size>
>> >        <node>0</node>
>> >      </target>
>> >      <alias name='nvdimm0'/>
>> >      <address type='dimm' slot='0'/>
>> >    </memory>
>> >
>> 
>> I am not familiar with virsh, while I guess align here is the parameter 
>> passed
>> to qemu.
>> 
>> Hmm...  as I being told, the alignment should be 128M.
>2MB align is OK for this case.

Ok, so would you mind putting more word on the alignment?

Which case requires 128M and which requires 2M?

I got lost here.

-- 
Wei Yang
Help you, Help me