[libvirt] [PATCH v1] libxl: reverse defaults on HVM net device attach

[Jim Fehlig]

On 12/14/2016 03:53 AM, Joao Martins wrote:
> libvirt libxl picks its own default with respect to the default NIC
> to use. libxlMakeNic is the one responsible for this and on boot it
> picks LIBXL_NIC_TYPE_VIF_IOEMU for HVM domains such that it accomodates
> both PV and emulated one. The good behaving guest at boot will then
> select the pv and unplug the emulated device.
>
> Now, on HVM when attaching an interface it will pick the same default
> that is LIBXL_NIC_TYPE_VIF_IOEMU which as a result will fail the attach
> (see xen commit 32e9d0f ("libxl: nic type defaults to vif in hotplug for
> hvm guest"). Xen doesn't yet support the hotplug of emulated devices,
> but we don't want to rule out that case either, which might get support
> in the future. Hence we simply reverse the defaults when we are
> attaching the interface which allows libvirt to prefer the PV nic first
> without adding "model='netfront'" following the same pattern as above
> commit. Also to avoid ruling out the emulated one we set to
> LIBXL_NIC_TYPE_IOEMU when setting a model type that is not 'netfront'.
>
> Signed-off-by: Joao Martins <joao.m.martins at oracle.com>
> Signed-off-by: Jim Fehlig <jfehlig at suse.com>
> ---
> Since RFC:
> - Joao: Add mention to HVM domains in the first paragraph of commit
>         message.
> - Jim: Add comment about libxl_device_nic type inner workings
> - Jim: Prevent attach on PV when model != netfront
> - Joao: Remove now unused ioemu_nic variable
> - Joao: Append one small paragraph about why we mimic xl/libxl
> ---
>  src/libxl/libxl_conf.c   | 39 +++++++++++++++++++++++++++++++--------
>  src/libxl/libxl_conf.h   |  3 ++-
>  src/libxl/libxl_driver.c |  2 +-
>  3 files changed, 34 insertions(+), 10 deletions(-)

ACK and pushed.

Regards,
Jim