Re: [PATCH for-next] RDMA/nldev: Add parent bdf to device information dump

[Gal Pressman <galpress@amazon.com>]

On 09/11/2020 1:49, Jason Gunthorpe wrote:
> On Sun, Nov 08, 2020 at 03:03:45PM +0200, Gal Pressman wrote:
>> On 05/11/2020 22:00, Jason Gunthorpe wrote:
>>> On Tue, Nov 03, 2020 at 05:45:26PM +0200, Gal Pressman wrote:
>>>> On 03/11/2020 16:22, Jason Gunthorpe wrote:
>>>>> On Tue, Nov 03, 2020 at 04:11:19PM +0200, Gal Pressman wrote:
>>>>>> On 03/11/2020 15:57, Leon Romanovsky wrote:
>>>>>>> On Tue, Nov 03, 2020 at 09:45:22AM -0400, Jason Gunthorpe wrote:
>>>>>>>> On Tue, Nov 03, 2020 at 03:26:27PM +0200, Gal Pressman wrote:
>>>>>>>>> Add the ability to query the device's bdf through rdma tool netlink
>>>>>>>>> command (in addition to the sysfs infra).
>>>>>>>>>
>>>>>>>>> In case of virtual devices (rxe/siw), the netdev bdf will be shown.
>>>>>>>>
>>>>>>>> Why? What is the use case?
>>>>>>>
>>>>>>> Right, and why isn't netdev (RDMA_NLDEV_ATTR_NDEV_NAME) enough?
>>>>>>
>>>>>> When taking system topology into consideration you need some way to pair the
>>>>>> ibdev and bdf, especially when working with multiple devices.
>>>>>> The netdev name doesn't exist on devices with no netdevs (IB, EFA).
>>>>>
>>>>> You are supposed to use sysfs
>>>>>
>>>>> /sys/class/infiniband/ibp0s9/device
>>>>>
>>>>> Should always be the physical device
>>>>>
>>>>>> Why rdma tool? Because it's more intuitive than sysfs.
>>>>>
>>>>> But we generally don't put this information into netlink BDF is just
>>>>> the start, you need all the other topology information to make sense
>>>>> of it, and all that is in sysfs only already
>>>>
>>>> As the commit message says, it's in addition to the device sysfs.
>>>>
>>>> Many (if not most) of the existing rdma netlink commands are duplicates of some
>>>> sysfs entries, but show it in a more "modern" way.
>>>> I'm not convinced that bdf should be treated differently.
>>>
>>> Why did you call it BDF anyhow? it has nothing to do with PCI BDF
>>> other than it happens to be the PDF for PCI devices. Netdev called
>>> this bus_info
>>
>> Are there non pci devices in the subsystem?
> 
> Yes, HNS uses non-pci devices
> 
>> I can rename to a more fitting name, will change to bus_info unless
>> someone has a better idea.
> 
> The thing is, is is still useless. You have to consult sysfs to
> understand what bus it is scoped on to do anything further with
> it. Can't just assume it is PCI.

This can be solved with Parav's suggestion.