Re: [libvirt] [PATCH v5 02/11] nvdimm: introduce 'pmem' element into xml for NVDIMM memory

20 Dec 2018

$SUBJ:

conf: Introduce

On 12/20/18 4:14 AM, Luyao Zhong wrote:
...
The 'pmem' option allows users to specify whether the backend
storage of memory-backend-file is a real persistent memory:
<devices>
  ...
  <memory model='nvdimm' access='shared'>
      <source>
          <path>/dev/dax0.0</path>
          <pmem/>
      </source>
      <target>
          <size unit='MiB'>4094</size>
          <node>0</node>
          <label>
              <size unit='MiB'>2</size>
          </label>
      </target>
  </memory>
  ...
</devices>
Signed-off-by: Luyao Zhong <luyao.zhong@intel.com>
---
 docs/formatdomain.html.in                          | 12 +++++
 docs/schemas/domaincommon.rng                      |  5 ++
 src/conf/domain_conf.c                             | 13 +++++
 src/conf/domain_conf.h                             |  1 +
 .../memory-hotplug-nvdimm-pmem.xml                 | 58 ++++++++++++++++++++++
 .../memory-hotplug-nvdimm-pmem.xml                 |  1 +
 tests/qemuxml2xmltest.c                            |  1 +
 7 files changed, 91 insertions(+)
 create mode 100644 tests/qemuxml2argvdata/memory-hotplug-nvdimm-pmem.xml
 create mode 120000 tests/qemuxml2xmloutdata/memory-hotplug-nvdimm-pmem.xml

diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
index 515e656..0781f24 100644
--- a/docs/formatdomain.html.in
+++ b/docs/formatdomain.html.in
@@ -8323,6 +8323,7 @@ qemu-kvm -net nic,model=? /dev/null
     <source>
       <path>/tmp/nvdimm</path>
       <alignsize unit='KiB'>2048</alignsize>
+      <pmem/>
Should a whole new entry be created, e.g. rather than modifying the
above use:

  <memory model='nvdimm'>
    <source>
      <path>/dev/dax0.0</path>
      <pmem/>
    </source>
    <target>
      <size unit='KiB'>524288</size>
      <node>1</node>
      <label>
        <size unit='KiB'>128</size>
      </label>
    </target>
  </memory>

?

Whether the <target> values make sense or not is something you can clarify.
...
</source>
     <target>
       <size unit='KiB'>524288</size>
@@ -8423,6 +8424,17 @@ qemu-kvm -net nic,model=? /dev/null
               <span class="since">Since 5.0.0</span>
             </p>
           </dd>
+
+          <dt><code>pmem</code></dt>
+          <dd>
+            <p>
+              This element can be used to specify whether the backend storage
+              of memory-backend-file is a real persistent memory. If the
+              backend is a real persistence memory and <code>pmem</code> is set,
+              QEMU will guarantee the persistence of its own writes to the
+              vNVDIMM backend. <span class="since">Since 5.0.0</span>
Not sure exactly how to rewrite the above to be more hypervisor
agnostic, but how's this?:

If persistent memory is supported and enabled by the hypervisor in order
to guarantee the persistence of writes to the vNVDIMM backend, then use
the <code>pmem</code> element in order to utilize the feature.

I can make the changes with your OK.

Reviewed-by: John Ferlan <jferlan@redhat.com>

John

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