On 01/05/2011 05:19 AM, Daniel P. Berrange wrote:
We should try to keep terminology matching the disk<driver>
so I think
<driver name='qemu|vhost'/>
with omission of<driver> resulting in us automatically
adding either 'qemu' or 'vhost' to the XML. We don't
want to have an explicit 'default' value in the XML,
because users should be able to see the guest is running
with.
Do you mean to add it to the XML that's saved in the config? If so, that
would mean that it would only be possible to configure it as "use
whatever is best for the current situation" for the first startup of the
domain. Once that happened, it would be stuck on whichever was used the
first time (qemu or vhost), so if the domain was first started when
vhost-net was loaded, then later restarted when vhost-net wasn't loaded
(or maybe migrated to another host that didn't have vhost support), it
would fail to start.
If you mean adding it only to the dumpxml output (when the domain is
running, and --inactive isn't specified), I suppose that would be okay,
as long as there's an easy way for the low level functions to understand
that's the case.
Aside from that, I'd been thinking that the "backend" driver in this
case is virtio, not qemu or vhost; qemu(userland) vs vhost seems like
just a setting within that driver. So it doesn't seem appropriate to me
to have the name decide whether to use userland or vhost.
One other twist - there's already another request for something else to
be set for each network device: sndbuf.
<https://bugzilla.redhat.com/show_bug.cgi?id=665293>
https://bugzilla.redhat.com/show_bug.cgi?id=665293
<https://bugzilla.redhat.com/show_bug.cgi?id=665293>
The sndbuf setting is applicable to any network device that connects to
the real world using a tap device (ie, not just virtio). If we want to
add that setting via the same scheme, we would need something like:
<driver name='qemu|vhost' sndbuf='0'/>
(0 can't be the default, because 0 is actually one of the settings that
they want to explicitly specify (if sndbuf isn't given on the
commandline, qemu defaults to 1048576).
But what of the case where the device isn't virtio? Would you then
specify a <driver> with no name attribute? (eg "<driver sndbuf='0'/>)
--
libvir-list mailing list
libvir-list@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/libvir-list