Re: [PATCH 9/9] ib_verbs: Add a new qp create flag to request features for Ethernet over IB

[Santosh Shilimkar <santosh.shilimkar-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>]

On 9/2/2016 4:00 AM, Knut Omang wrote:
> On Fri, 2016-09-02 at 07:04 +0200, Knut Omang wrote:
>> On Thu, 2016-09-01 at 20:17 -0600, Jason Gunthorpe wrote:
>>>
>>> On Fri, Sep 02, 2016 at 02:09:29AM +0200, Knut Omang wrote:
>>>>
>>>> Some Infiniband HCAs need to know if a QP is going to
>>>> be used for Ethernet over IB (EOIB).
>>> You will have to send this after your driver. I recommend a patch
>>> proposing this functionality with your driver as the example
>>> implementation, along with a kernel user, as mellanox typically does.
>> It's a bit of a chicken and egg situation since the driver
>> depends on the patches. If I can 'tick off' this bit soon, I can move ahead and
>> get to the send the driver too.
>>
>> There's not much info in the driver - it just forwards that bit to a hardware bit
>> and it all happens from there. But hardware needs to know when to set that bit,
>> as it is only valid when operating as transport for Ethernet.
>>
Right. It comes down to removing mask filter at verbs layer and letting 
driver get the full view of it so that it can better deal with it based
on information.

>> Please - it would be a big help for me (saving a lot of work down the line that
>> is better spent working with the community than with handling more version issues later)
>> if I can get an indication that just that bit would be acceptable 8-D ...
>
> I will add the following further justification to the commit message for v2:
>
> Support for encapsulation of Ethernet over IB (EoIB) is a generic feature
> where different HCA implementations can include different special features.
> One example is that if the HCA knows the QP is going to be used for Ethernet,
> the implementation can ensure that all messages sent on this QP represents
> a properly formatted encapsulation of Ethernet frames with legal header values.
> Or the HCA can perform the encapsulation itself.
>
Don't want to hijack your patch but I also have seen another need where
ULP needs to pass additional information to driver for creating
RC qp with couple of add-ons . My current thought is to use reserved
QP flag bits (bits 26-31, for low level drivers' internal use) but
wanted to check if there is any objection to it.

Regards,
Santosh


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