Hello Stefan,
On Wednesday 21 March 2012 09:24:04 Stefan Bader wrote:
Unfortunately not true. You always get the enulated NIC, whatever you
do
with type=ioemu.
...
From what I see (and at least from Xen side expect) is that you
always get
both. Whether you use default or a specific NIC type. The only way for your
guest not to get an emulated device is to disable the pci-platform device
in the config.
Otherwise the Xen approach is to always present both and let the guest
decide whether it is capable of using the pv devices (which are faster).
Then the guest unplugs the emulated devices so there is no confusion. The
goal there is to have one configuration on the hosting side which allows
the guest to switch as it is capable.
So currently with the default setting for the NIC, you get the implicit
model or rtl8139 and the paravirt NIC. Newer Linux guests will, if they
think they can handle paravirt devices, unplug the emulated interfaces
(NICs and disks). I would expect a similar behavior from the Windows
drivers. So with the default, there should be no need to change the model.
However with the current libvirt, when you do select something like e1000,
then the Xen configuration gets a type=ioemu added. But that does _not_
prevent the paravirt interface to be present, its "just" unusable because
it does not have a MAC address.
Yes, you're correct. Now that you mention the MAC adress, I remember seeing
the netfront device with an all-zero-MAC-adress. I started writing the
attached email some time ago, but never sent it because the libvirt behaviour
was understandable and consistent: "If you specify a model, you only what
that model (and not the netfront as well)".
That this behaviour makes switching from emulated to PV more complicates, is a
different matter. I would appreciate a change in that behaviour as well, so
+1 for your work.
Sincerely
Philipp
--
Philipp Hahn Open Source Software Engineer hahn(a)univention.de
Univention GmbH be open. fon: +49 421 22 232- 0
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