[libvirt] [REPOSTv2 PATCH v3 1/6] conf: Add VM Generation ID parse/format support

[Michal Privoznik]

On 05/17/2018 02:42 PM, John Ferlan wrote:
> The VM Generation ID is a mechanism to provide a unique 128-bit,
> cryptographically random, and integer value identifier known as
> the GUID (Globally Unique Identifier) to the guest OS. The value
> is used to help notify the guest operating system when the virtual
> machine is executed with a different configuration.
> 
> This patch adds support for a new "genid" XML element similar to
> the "uuid" element. The "genid" element can have two forms "<genid/>"
> or "<genid>$GUID</genid>". If the $GUID is not provided, libvirt
> will generate one and save it in the XML.
> 
> Since adding support for a generated GUID (or UUID like) value to
> be displayed modifying the xml2xml test to include virrandommock.so
> is necessary since it will generate a "known" value.
> 
> Signed-off-by: John Ferlan <jferlan at redhat.com>
> ---
>  docs/formatdomain.html.in                        | 27 ++++++++++++
>  docs/schemas/domaincommon.rng                    |  8 ++++
>  src/conf/domain_conf.c                           | 54 ++++++++++++++++++++++++
>  src/conf/domain_conf.h                           |  5 +++
>  tests/qemuxml2argvdata/genid-auto.xml            | 32 ++++++++++++++
>  tests/qemuxml2argvdata/genid.xml                 | 32 ++++++++++++++
>  tests/qemuxml2xmloutdata/genid-active.xml        | 32 ++++++++++++++
>  tests/qemuxml2xmloutdata/genid-auto-active.xml   | 32 ++++++++++++++
>  tests/qemuxml2xmloutdata/genid-auto-inactive.xml | 32 ++++++++++++++
>  tests/qemuxml2xmloutdata/genid-inactive.xml      | 32 ++++++++++++++
>  tests/qemuxml2xmltest.c                          |  5 ++-
>  11 files changed, 290 insertions(+), 1 deletion(-)
>  create mode 100644 tests/qemuxml2argvdata/genid-auto.xml
>  create mode 100644 tests/qemuxml2argvdata/genid.xml
>  create mode 100644 tests/qemuxml2xmloutdata/genid-active.xml
>  create mode 100644 tests/qemuxml2xmloutdata/genid-auto-active.xml
>  create mode 100644 tests/qemuxml2xmloutdata/genid-auto-inactive.xml
>  create mode 100644 tests/qemuxml2xmloutdata/genid-inactive.xml
> 
> diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
> index 0d0fd3b9f3..72a55ff075 100644
> --- a/docs/formatdomain.html.in
> +++ b/docs/formatdomain.html.in
> @@ -34,6 +34,7 @@
>  <domain type='kvm' id='1'>
>    <name>MyGuest</name>
>    <uuid>4dea22b3-1d52-d8f3-2516-782e98ab3fa0</uuid>
> +  <genid>43dc0cf8-809b-4adb-9bea-a9abb5f3d90e</genid>
>    <title>A short description - title - of the domain</title>
>    <description>Some human readable description</description>
>    <metadata>
> @@ -61,6 +62,32 @@
>          specification. <span class="since">Since 0.0.1, sysinfo
>          since 0.8.7</span></dd>
>  
> +      <dt><code>genid</code></dt>
> +      <dd><span class="since">Since 4.4.0</span>, the <code>genid</code>
> +        element can be used to add a Virtual Machine Generation ID which
> +        exposes a 128-bit, cryptographically random, integer value identifier,
> +        referred to as a Globally Unique Identifier (GUID) using the same
> +        format as the <code>uuid</code>. The value is used to help notify
> +        the guest operating system when the virtual machine is re-executing
> +        something that has already executed before, such as:
> +
> +        <ul>
> +          <li>VM starts executing a snapshot</li>
> +          <li>VM is recovered from backup</li>
> +          <li>VM is failover in a disaster recovery environment</li>
> +          <li>VM is imported, copied, or cloned</li>
> +        </ul>
> +
> +        The guest operating system notices the change and is then able to
> +        react as appropriate by marking its copies of distributed databases
> +        as dirty, re-initializing its random number generator, etc.
> +
> +        <p>
> +        The libvirt XML parser will accept both a provided GUID value
> +        or just <genid/> in which case a GUID will be generated
> +        and saved in the XML. For the transitions such as above, libvirt
> +        will change the GUID before re-executing.</p></dd>
> +
>        <dt><code>title</code></dt>
>        <dd>The optional element <code>title</code> provides space for a
>          short description of the domain. The title should not contain
> diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng
> index 71ac3d079c..1fba108927 100644
> --- a/docs/schemas/domaincommon.rng
> +++ b/docs/schemas/domaincommon.rng
> @@ -502,6 +502,14 @@
>            <ref name="UUID"/>
>          </element>
>        </optional>
> +      <optional>
> +        <element name="genid">
> +          <choice>
> +            <ref name="UUID"/>
> +            <empty/>
> +          </choice>
> +        </element>
> +      </optional>
>      </interleave>
>    </define>
>    <define name="idmap">
> diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
> index 3689ac0a82..4d5f3c6740 100644
> --- a/src/conf/domain_conf.c
> +++ b/src/conf/domain_conf.c
> @@ -18919,6 +18919,34 @@ virDomainDefParseXML(xmlDocPtr xml,
>          VIR_FREE(tmp);
>      }
>  
> +    /* Extract domain genid - a genid can either be provided or generated */
> +    if ((n = virXPathNodeSet("./genid", ctxt, &nodes)) < 0)
> +        goto error;
> +
> +    if (n > 0) {
> +        if (n != 1) {
> +            virReportError(VIR_ERR_XML_ERROR, "%s",
> +                          _("element 'genid' can only appear once"));

This _() seems misaligned.

> +            goto error;
> +        }
> +        def->genidRequested = true;
> +        if (!(tmp = virXPathString("string(./genid[1])", ctxt))) {

Since you check that there's only onde <genid/> above, this [1] seems
redundant.

> +            if (virUUIDGenerate(def->genid) < 0) {
> +                virReportError(VIR_ERR_INTERNAL_ERROR,
> +                               "%s", _("Failed to generate genid"));
> +                goto error;
> +            }
> +            def->genidGenerated = true;
> +        } else {
> +            if (virUUIDParse(tmp, def->genid) < 0) {
> +                virReportError(VIR_ERR_INTERNAL_ERROR,
> +                               "%s", _("malformed genid element"));
> +                goto error;
> +            }
> +        }
> +    }
> +    VIR_FREE(nodes);
> +

Michal