Re: error loading xdp program on virtio nic

[Jason Wang <jasowang@redhat.com>]

On 2019/11/21 上午11:35, David Ahern wrote:
> On 11/20/19 8:26 PM, Jason Wang wrote:
>> On 2019/11/21 上午1:52, David Ahern wrote:
>>> Hi:
>>>
>>> Trying to load an XDP program on a virtio based nic is failing with:
>>>
>>> virtio_net: XDP expects header/data in single page, any_header_sg
>>> required
>>>
>>> I have not encountered this error before and not able to find what is
>>> missing. Any tips?
>>
>> Hi David:
>>
>> What qemu + guest kernel version did you use? And could you share you
>> qemu cli?
>>
>> Old qemu requires vnet header to be placed into a separate sg which
>> breaks the assumption of XDP. Recent qemu doesn't have such limitation
>> (any_header_sg feature).
>>
>>
> Hi Jason,
>
> When I run qemu via my older vm-tools scripts XDP works fine. This is
> the first time I am trying to use XDP with guests started by libvirt.
>
> We isolated it to a libvirt xml file using an old machine type
> (pc-i440fx-1.5) - basically any machine with VIRTIO_F_VERSION_1 not set.
> Using a newer one move the problem forward.


Yes, if VERSION_1 implies ANY_HEADER_SG, and if you're using old qemu, 
make sure any_header_sg is enabled in qemu cli.


>
> The current error message is:
>    virtio_net: Too few free TX rings available
> again, looking for some libvirt setting for the vm create.
>

Make sure you have sufficient queues, e.g if you N vcpus with multiqueue 
enabled, you need 2*N queues for virtio-net.

Thanks