[libvirt] [PATCH v3 08/17] conf: Introduce @access to <memory/>

[John Ferlan]

On 03/09/2017 11:06 AM, Michal Privoznik wrote:
> Now that NVDIMM has found its way into libvirt, users might want
> to fine tune some settings for each module separately. One such
> setting is 'share=on|off' for the memory-backend-file object.
> This setting - just like its name suggest already - enables
> sharing the nvdimm module with other applications. Under the hood
> it controls whether qemu mmaps() the file as MAP_PRIVATE or
> MAP_SHARED.
> 
> Yet again, we have such config knob in domain XML, but it's just
> an attribute to numa <cell/>. This does not give fine enough
> tuning on per-memdevice basis so we need to have the attribute
> for each device too.
> 
> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
> ---
>  docs/formatdomain.html.in                          | 16 ++++++-
>  docs/schemas/domaincommon.rng                      |  8 ++++
>  src/conf/domain_conf.c                             | 15 +++++-
>  src/conf/domain_conf.h                             |  2 +
>  .../qemuxml2argv-memory-hotplug-nvdimm-access.xml  | 56 ++++++++++++++++++++++
>  ...qemuxml2xmlout-memory-hotplug-nvdimm-access.xml |  1 +
>  tests/qemuxml2xmltest.c                            |  1 +
>  7 files changed, 96 insertions(+), 3 deletions(-)
>  create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-memory-hotplug-nvdimm-access.xml
>  create mode 120000 tests/qemuxml2xmloutdata/qemuxml2xmlout-memory-hotplug-nvdimm-access.xml
> 

This patch fails make check for me because your qemuxml2xmloutdata has
the wrong softlink set up.  I don't have "/home/zippy/work/...", but I
would have

e.g. from the tests/qemuxml2xmloutdata directory use:

ln -sf ../qemuxml2argvdata/qemuxml2argv-memory-hotplug-nvdimm-access.xml
qemuxml2xmlout-memory-hotplug-nvdimm-access.xml

> diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
> index 6e89bfe3a..4bc3d92f9 100644
> --- a/docs/formatdomain.html.in
> +++ b/docs/formatdomain.html.in
> @@ -1417,7 +1417,7 @@
>        <span class='since'>Since 1.2.9</span> the optional attribute
>        <code>memAccess</code> can control whether the memory is to be
>        mapped as "shared" or "private".  This is valid only for
> -      hugepages-backed memory.
> +      hugepages-backed memory and nvdimm modules.
>      </p>
>  
>      <p>
> @@ -7099,7 +7099,7 @@ qemu-kvm -net nic,model=? /dev/null
>  <pre>
>  ...
>  <devices>
> -  <memory model='dimm'>
> +  <memory model='dimm' access='private'>
>      <target>
>        <size unit='KiB'>524287</size>
>        <node>0</node>
> @@ -7138,6 +7138,18 @@ qemu-kvm -net nic,model=? /dev/null
>          </p>
>        </dd>
>  
> +      <dt><code>access</code></dt>
> +      <dd>
> +        <p>
> +          An optional attribute <code>access</code>
> +          (<span class="since">since 3.2.0</span>) that provides
> +          capability to fine tune mapping of the memory on per
> +          module basis. Values are the same as
> +          <a href="#elementsMemoryBacking">Memory Backing</a>:
> +          <code>shared</code> and <code>private</code>.
> +        </p>
> +      </dd>
> +

>From the v2 code review comment/response - can/should we state right
here that the access setting in/for nvdimm would override any
memoryBacking setting?'

If so, then would it be furthermore interesting to modify the XML here
to set the memoryBacking as private and override that, but it's not
required...

ACK w/ the fixed link to the output file... Your call on the doc change


John