Re: [Qemu-devel] [virtio-dev] [PATCH 4/4] virtio-net: add linkspeed and duplex settings to virtio-net

[Yan Vugenfirer]

> On 6 Mar 2018, at 20:13, Michael S. Tsirkin <address@hidden> wrote:
> 
> On Tue, Mar 06, 2018 at 01:02:06PM -0500, Jason Baron wrote:
>> 
>> 
>> On 03/04/2018 08:05 AM, Yan Vugenfirer wrote:
>>> 
>>> 
>>>> On 2 Mar 2018, at 22:19, Michael S. Tsirkin <address@hidden
>>>> <mailto:address@hidden>> wrote:
>>>> 
>>>> On Fri, Mar 02, 2018 at 03:14:01PM +0800, Jason Wang wrote:
>>>>> 
>>>>> 
>>>>> On 2018年03月02日 11:46, Jason Baron wrote:
>>>>>> Although linkspeed and duplex can be set in a linux guest via
>>>>>> 'ethtool -s',
>>>>>> this requires custom ethtool commands for virtio-net by default.
>>>>>> 
>>>>>> Introduce a new feature flag, VIRTIO_NET_F_SPEED_DUPLEX, which allows
>>>>>> the hypervisor to export a linkspeed and duplex setting. The user can
>>>>>> subsequently overwrite it later if desired via: 'ethtool -s'.
>>>>>> 
>>>>>> Linkspeed and duplex settings can be set as:
>>>>>> '-device virtio-net,speed=10000,duplex=full'
>>>>> 
>>>>> I was thinking whether or not it's better to decide the duplex by the
>>>>> type
>>>>> of backends.
>>>>> 
>>>>> E.g userspace and vhost-kernel implement a in fact half duplex. But dpdk
>>>>> implement a full duplex.
>>>>> 
>>>>> Thanks
>>>> 
>>>> OTOH it's a priority for some people to be able to support migration
>>>> between different backend types. Breaking that won't be nice.
>>> 
>>> I think that in this case we need a way to update the settings of link
>>> speed and link duplex (maybe add QMP command). Migration between
>>> different backend types should cause link down\link up events. And this
>>> is a time for a driver to re-read the settings and update the OS.
>>> 
>>> Best regards,
>>> Yan.
>>> 
>> 
>> So the virtio_net driver in linux will re-read these settings on link up
>> events. So I could add a qmp command to set these (in addition to the
>> command-line) interface, if desired. Is there a consensus that we need
>> to add a qmp command here? Or can that be treated as a future item, if
>> somebody wants it?
>> 
>> Thanks,
>> 
>> -Jason
> 
> We already have ability to take link down and up.
> I'd say it's a future item.
I agree.

Yan.
> 
> -- 
> MST