Steps to reproduce:
1. Start with powered off VM.
2. Use 'virsh edit domain' to add the line <driver cache='none'/> to each <disk> clause.
3. Run 'virsh dumpxml domain' and note that the cache lines you just added have disappeared.
4. Start the domain and look at the kvm command line. It includes the cache=none option on the appropriate -disk options.
5. Stop the domain.
6. Use 'virsh edit domain' to make an unrelated change (e.g. memory size).
7. Because the <driver cache='none'/> lines were no longer there, the cache options are removed next time the domain is booted.
Expected behavior:
The <driver cache='none'/> line stays in the file just like every other valid option.
I'm really confused as to where libvirt is storing the fact that I disabled the cache, since it does take effect despite disappearing from the XML file.
Ubuntu Karmic, libvirt 0.7.0-1ubuntu13.
On Thu, Mar 04, 2010 at 05:59:24AM -0000, Benjamin Jencks wrote:
> I'm really confused as to where libvirt is storing the fact that I
> disabled the cache, since it does take effect despite disappearing
> from the XML file.
When you hand an XML file to libvirt (e.g. with "virsh define"), it
parses it, stores the information in a (set of) C struct(s), and throws
the XML away. When you read it back, libvirt takes the information from
the (set of) C struct(s) and creates an XML file from this information.
Based on what you're saying, it sounds like libvirt correctly parses the
cache tag and acts on it, but the routine to generate the XML inside
libvirt is missing the few lines of code to serialise this information
in the XML file.
--
Soren Hansen
Ubuntu Developer
http://