Re: [PATCH linux-next v3 6/6] vdpa_sim_net: Add support for user supported devices

From: Jason Wang <jasowang@redhat.com>
To: Parav Pandit <parav@nvidia.com>, "Michael S. Tsirkin" <mst@redhat.com>
Cc: "virtualization@lists.linux-foundation.org" 
	<virtualization@lists.linux-foundation.org>,
	Eli Cohen <elic@nvidia.com>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>
Subject: Re: [PATCH linux-next v3 6/6] vdpa_sim_net: Add support for user supported devices
Date: Thu, 14 Jan 2021 12:17:53 +0800
Message-ID: <66dc44ac-52da-eaba-3f5e-69254e42d75b@redhat.com> (raw)
In-Reply-To: <BY5PR12MB4322EC8D0AD648063C607E17DCAF0@BY5PR12MB4322.namprd12.prod.outlook.com>

On 2021/1/7 上午11:48, Parav Pandit wrote:
>
>> From: Michael S. Tsirkin <mst@redhat.com>
>> Sent: Tuesday, January 5, 2021 6:53 PM
>>
>> On Tue, Jan 05, 2021 at 12:30:15PM +0000, Parav Pandit wrote:
>>>
>>>> From: Michael S. Tsirkin <mst@redhat.com>
>>>> Sent: Tuesday, January 5, 2021 5:45 PM
>>>>
>>>> On Tue, Jan 05, 2021 at 12:02:33PM +0000, Parav Pandit wrote:
>>>>>
>>>>>> From: Michael S. Tsirkin <mst@redhat.com>
>>>>>> Sent: Tuesday, January 5, 2021 5:19 PM
>>>>>>
>>>>>> On Tue, Jan 05, 2021 at 12:32:03PM +0200, Parav Pandit wrote:
>>>>>>> Enable user to create vdpasim net simulate devices.
>>>>>>>
>>>>>>>
>>>>>>> $ vdpa dev add mgmtdev vdpasim_net name foo2
>>>>>>>
>>>>>>> Show the newly created vdpa device by its name:
>>>>>>> $ vdpa dev show foo2
>>>>>>> foo2: type network mgmtdev vdpasim_net vendor_id 0 max_vqs 2
>>>>>>> max_vq_size 256
>>>>>>>
>>>>>>> $ vdpa dev show foo2 -jp
>>>>>>> {
>>>>>>>      "dev": {
>>>>>>>          "foo2": {
>>>>>>>              "type": "network",
>>>>>>>              "mgmtdev": "vdpasim_net",
>>>>>>>              "vendor_id": 0,
>>>>>>>              "max_vqs": 2,
>>>>>>>              "max_vq_size": 256
>>>>>>>          }
>>>>>>>      }
>>>>>>> }
>>>>>>
>>>>>> I'd like an example of how do device specific (e.g. net
>>>>>> specific) interfaces tie in to this.
>>>>> Not sure I follow your question.
>>>>> Do you mean how to set mac address or mtu of this vdpa device of
>>>>> type
>>>> net?
>>>>> If so, dev add command will be extended shortly in subsequent
>>>>> series to
>>>> set this net specific attributes.
>>>>> (I did mention in the next steps in cover letter).
>>>>>
>>>>>>> +static int __init vdpasim_net_init(void) {
>>>>>>> +	int ret;
>>>>>>> +
>>>>>>> +	if (macaddr) {
>>>>>>> +		mac_pton(macaddr, macaddr_buf);
>>>>>>> +		if (!is_valid_ether_addr(macaddr_buf))
>>>>>>> +			return -EADDRNOTAVAIL;
>>>>>>> +	} else {
>>>>>>> +		eth_random_addr(macaddr_buf);
>>>>>>>   	}
>>>>>> Hmm so all devices start out with the same MAC until changed?
>>>>>> And how is the change effected?
>>>>> Post this patchset and post we have iproute2 vdpa in the tree,
>>>>> will add the
>>>> mac address as the input attribute during "vdpa dev add" command.
>>>>> So that each different vdpa device can have user specified
>>>>> (different) mac
>>>> address.
>>>>
>>>> For now maybe just avoid VIRTIO_NET_F_MAC then for new devices
>> then?
>>> That would require book keeping existing net vdpa_sim devices created to
>> avoid setting VIRTIO_NET_F_MAC.
>>> Such book keeping code will be short lived anyway.
>>> Not sure if its worth it.
>>> Until now only one device was created. So not sure two vdpa devices with
>> same mac address will be a real issue.
>>> When we add mac address attribute in add command, at that point also
>> remove the module parameter macaddr.
>>
>> Will that be mandatory? I'm not to happy with a UAPI we intend to break
>> straight away ...
> No. Specifying mac address shouldn't be mandatory. UAPI wont' be broken.

If it's not mandatory. Does it mean the vDPA parent need to use its own 
logic to generate a validate mac? I'm not sure this is what management 
(libvirt want).

Thanks

>