Re: [PATCH 1/1] RDMA/mlx5: Make mlx5 device work with ib_device_get_by_netdev

[Yanjun Zhu <yanjun.zhu@linux.dev>]

在 2022/10/19 19:55, Jason Gunthorpe 写道:
> On Wed, Oct 19, 2022 at 09:08:14AM +0000, yanjun.zhu@linux.dev wrote:
>> October 18, 2022 4:24 PM, "Leon Romanovsky" <leon@kernel.org> wrote:
>>
>>> On Sun, Oct 16, 2022 at 02:19:25AM -0400, Zhu Yanjun wrote:
>>>
>>>> From: Zhu Yanjun <yanjun.zhu@linux.dev>
>>>>
>>>> Before mlx5 ib device is registered, the function ib_device_set_netdev
>>>> is not called to map the mlx5 ib device with the related net device.
>>>>
>>>> As such, when the function ib_device_get_by_netdev is called to get ib
>>>> device, NULL is returned.
>>>>
>>>> Other ib devices, such as irdma, rxe and so on, the function
>>>> ib_device_get_by_netdev can get ib device from the related net device.
>>> Ohh, you opened Pandora box, everything around it looks half-backed.
>>>
>>> mlx4 and mlx5 don't call to ib_device_set_netdev(), because they have
>>> .get_netdev() callback. This callback is not an easy task to eliminate
>>> and many internal attempts failed to eliminate them.
>>>
>>> This caused to very questionable ksmbd_rdma_capable_netdev()
>>> implementation where ksmbd first checked internal ib_dev callback
>>> and tried to use ib_device_get_by_netdev(). And to smc_ib, which
>>> didn't even bother to use ib_device_get_by_netdev().
>> Thanks.
>>
>> I read the function ksmbd_rdma_capable_netdev carefully.
>> Mlx5 and mlx4 do not call ib_device_set_netdev to map net device and ib devices.
>> This brings a lot of problems.
> ULPs are not allowed to use these interfaces, they are for driver
> implementations.
>
> It is an error that ksmbd_rdma_capable_netdev() calls it in the first
> place.

Got it.  The following function should complete the same job.

Maybe we can use this function to implement ksmbd_rdma_capable_netdev again.

int ib_enum_all_devs(nldev_callback nldev_cb, struct sk_buff *skb,
                      struct netlink_callback *cb)


Thanks and Regards,

Zhu Yanjun

>
> Jason