Re: [libvirt] [PATCHv2 0/3] Xen: Fix <clock> handling

9 Feb 2012

      On 02/09/2012 03:01 PM, Eric Blake wrote:
...
We absolutely cannot reject existing older xml files; but must load them
with the semantics that make sense.

...
But a better idea is to represent the XML in a way where the default
conversion makes sense, but where a user can explicitly change the XML
to get what they want.  I'm thinking:
If offset is 'utc' or 'localtime', we add a new attribute 'adjustment',
whose value can be either 'reset' to signify that the offset is reset on
each boot, or a timeDelta, as shorthand for specifying offset='variable'
adjustment='nnn' basis='utc|localtime'.  If the attribute is missing,
the hypervisor determines whether the default is 'reset' or '0'.  Qemu
would pick 'reset', xend would pick '0'.

...
RNG-wise, this would be:
I missed basis:
...
<element name='clock'>
        <choice>
          <group>
            <attribute name='offset'>
              <choice>
                <value>localtime</value>
                <value>utc</value>
              </choice>
            </attribute>
            <optional>
              <attribute name='adjustment'>
                <choice>
                  <ref name='timeDelta'/>
                  <value>reset</value>
                </choice>
              </attribute>
            </optional>
          </group>
          <group>
            <attribute name='offset'>
              <value>timezone</value>
            </attribute>
            <optional>
              <attribute name='timezone'>
                <ref name='timeZone'/>
              </attribute>
            </optional>
          </group>
          <group>
            <attribute name='offset'>
              <value>variable</value>
            </attribute>
            <optional>
              <attribute name='adjustment'>
                <ref name='timeDelta'/>
              </attribute>
            </optional>
<optional>
                <attribute name='basis'>
                  <choice>
                    <value>utc</value>
                    <value>localtime</value>
                  </choice>
                </attribute>
              </optional>
...
</group>
        </choice>
        <zeroOrMore>
          <ref name='timer'/>
        </zeroOrMore>
      </element>
-- 
Eric Blake   eblake@redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org