Re: [PATCH linux-next v3 0/6] vdpa: enable user to set mac, mtu

[Jason Wang <jasowang@redhat.com>]

在 2021/8/6 下午4:55, Parav Pandit 写道:
>
>> From: Michael S. Tsirkin <mst@redhat.com>
>> Sent: Friday, August 6, 2021 2:12 PM
>
>>>   enum vdpa_attr {
>>> @@ -33,6 +34,16 @@ enum vdpa_attr {
>>>   	VDPA_ATTR_DEV_MAX_VQS,			/* u32 */
>>>   	VDPA_ATTR_DEV_MAX_VQ_SIZE,		/* u16 */
>>> +	VDPA_ATTR_DEV_NET_CFG_MACADDR,		/* binary */
>>> +	VDPA_ATTR_DEV_NET_STATUS,		/* u8 */
>>> +	VDPA_ATTR_DEV_NET_CFG_MAX_VQP,		/* u16 */
>>> +	VDPA_ATTR_DEV_NET_CFG_MTU,		/* u16 */
>>> +	VDPA_ATTR_DEV_NET_CFG_SPEED,		/* u16 */
>>> +	VDPA_ATTR_DEV_NET_CFG_DUPLEX,		/* u16 */
>>> +	VDPA_ATTR_DEV_NET_CFG_RSS_MAX_KEY_LEN,	/* u8 */
>>> +	VDPA_ATTR_DEV_NET_CFG_RSS_MAX_IT_LEN,	/* u16 */
>>> +	VDPA_ATTR_DEV_NET_CFG_RSS_HASH_TYPES,	/* u32 */
>>> +
>>>   	/* new attributes must be added above here */
>>>   	VDPA_ATTR_MAX,
>>>   };
>> The point is to try and not reinvent a dedicated vpda interface where a
>> generic one exits.
>> E.g. for phy things such as mac speed etc, I think most people are using
>> ethtool things right?
> As you know vdpa is the backend device for the front-end netdevice accessed by the ethtool.
> vdpa management tool here is composing the vdpa device.
>
> For example creator (hypervisor) of the vdpa devices knows that a guest VM is given 4 vcpus,
> So hypervisor creates a vdpa devices with config space layout as,
> max_virtqueue_pairs = 4.
> And the MAC address chosen by hypervisor in mac[6].
>
> Guest VM ethtool can still chose to use less number of channels.
>
> Typically,
> ethtool is for guest VM.
> vdpa device is in hypevisor.
>
> How can hypervisor compose a vdpa device without any tool?
> How can it tell ethtool, what is supported and what are the defaults?


Reread the cover letter:

"

This patchset enables users to set the mac address and mtu of the vdpa
device once the device is created.

"

It looks to me the mechanism that introduced in the series is not for 
provisioning but for post-creation configuration?


>
> I must be misunderstanding your comment about ethtool.
> Can you please explain?


I guess the meaning is that, if the vDPA is assigned to guest, it's the 
charge of guest to configure the MTU/MAC/RSS via the existing management 
interface like ethtool/iproute2 netlink protocol. The control virtqueue 
is designed for this.

But if it was used for provisioning, it looks like another topic which 
should be done during the device creation.

Thanks


>

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