netdev - Re: [PATCH linux-next v2 4/7] vdpa: Define vdpa mgmt device, ops and a netlink interface

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Message-ID: <449d2860-c75f-04fa-9080-c99dc6df7288@redhat.com>
Date:   Tue, 5 Jan 2021 16:36:19 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Parav Pandit <parav@...dia.com>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>
Cc:     "mst@...hat.com" <mst@...hat.com>, Eli Cohen <elic@...dia.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH linux-next v2 4/7] vdpa: Define vdpa mgmt device, ops and
 a netlink interface


On 2021/1/5 下午2:33, Parav Pandit wrote:
>
>> From: Jason Wang <jasowang@...hat.com>
>> Sent: Tuesday, January 5, 2021 9:40 AM
>>
>> On 2021/1/4 下午3:24, Parav Pandit wrote:
>>>> From: Jason Wang <jasowang@...hat.com>
>>>> Sent: Monday, January 4, 2021 12:33 PM
>>>>
>>>> On 2021/1/4 上午11:31, Parav Pandit wrote:
>>>>> To add one or more VDPA devices, define a management device which
>>>>> allows adding or removing vdpa device. A management device defines
>>>>> set of callbacks to manage vdpa devices.
>>>>>
>>>>> To begin with, it defines add and remove callbacks through which a
>>>>> user defined vdpa device can be added or removed.
>>>>>
>>>>> A unique management device is identified by its unique handle
>>>>> identified by management device name and optionally the bus name.
>>>>>
>>>>> Hence, introduce routine through which driver can register a
>>>>> management device and its callback operations for adding and remove
>>>>> a vdpa device.
>>>>>
>>>>> Introduce vdpa netlink socket family so that user can query
>>>>> management device and its attributes.
>>>>>
>>>>> Example of show vdpa management device which allows creating vdpa
>>>>> device of networking class (device id = 0x1) of virtio specification
>>>>> 1.1 section 5.1.1.
>>>>>
>>>>> $ vdpa mgmtdev show
>>>>> vdpasim_net:
>>>>>      supported_classes:
>>>>>        net
>>>>>
>>>>> Example of showing vdpa management device in JSON format.
>>>>>
>>>>> $ vdpa mgmtdev show -jp
>>>>> {
>>>>>        "show": {
>>>>>            "vdpasim_net": {
>>>>>                "supported_classes": [ "net" ]
>>>>>            }
>>>>>        }
>>>>> }
>>>>>
>>>>> Signed-off-by: Parav Pandit<parav@...dia.com>
>>>>> Reviewed-by: Eli Cohen<elic@...dia.com>
>>>>> Reviewed-by: Jason Wang<jasowang@...hat.com>
>>>>> ---
>>>>> Changelog:
>>>>> v1->v2:
>>>>>     - rebased
>>>>>     - updated commit log example for management device name from
>>>>>       "vdpasim" to "vdpasim_net"
>>>>>     - removed device_id as net and block management devices are
>>>>> separated
>>>> So I wonder whether there could be a type of management devices that
>>>> can deal with multiple types of virtio devices. If yes, we probably
>>>> need to add device id back.
>>> At this point mlx5 plan to support only net.
>>> It is useful to see what type of vdpa device is supported by a management
>> device.
>>> In future if a mgmt dev supports multiple types, user needs to choose
>> desired type.
>>> I guess we can differ this optional type to future, when such mgmt. device
>> will/may be available.
>>
>>
>> I worry if we remove device_id, it may gives a hint that multiple mgmt
>> devices needs to be registered if it supports multiple types.
>>
> No it shouldn't. because we do expose multiple supported types in mgmtdev attributes.


Right.


>
>> So if possible I would like to keep the device_id here.
>>
> Its possible to keep it. But with current drivers, mainly mlx5 and vdpa_sim, it is redundant.
> Not sure of the ifc's plan.
> We have been splitting modules to handle net and block differently in mlx5 as well as vdpa_sim.
> So it looks to me that both may be separate management drivers (and management devices).
> Such as vdpasim_net and vdpasim_block.
> mlx5 doesn't have plan for block yet.


Ok. Then it's fine.

Thanks