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

[Yan Vugenfirer]

> On 2 Mar 2018, at 22:19, Michael S. Tsirkin <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.

> 
>>> 
>>> where speed is [0...INT_MAX], and duplex is ["half"|"full"].
>>> 
>>> Signed-off-by: Jason Baron<address@hidden>
>>> Cc: "Michael S. Tsirkin"<address@hidden>
>>> Cc: Jason Wang<address@hidden>
>>> Cc:address@hidden
>>> ---
> 
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