On 12/14/2016 08:53 PM, Jim Fehlig wrote:
> 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@xxxxxxxxxx>
>> Signed-off-by: Jim Fehlig <jfehlig@xxxxxxxx>
>> ---
>> 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.
Thank you!
Joao
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