[ofa-general] Re: How to tell what OFED rev a distro derived IB modules?

[Bart Van Assche]

On Sun, Apr 26, 2009 at 1:31 PM, Jack Morgenstein
<jackm at dev.mellanox.co.il> wrote:
> On Friday 24 April 2009 02:48, Jason Gunthorpe wrote:
>> AFAIK, Ubuntu does not do any work on their IB drivers, so the driver
>> is stock 2.6.27.
>>
>> In principle OFED is supposed to start with an upstream kernel and
>> backport those drivers to various distributions. OFED 1.3 was using
>> 2.6.24, OFED 1.4 is apparently using 2.6.27.
>>
>> So it should be similar to OFED 1.4
>>
>> Though bear in mind OFED still patches things with stuff that is not
>> yet accepted upstream so there will be some differences.
>>
>> It should be compatible with the OFED 1.4 userspace.
>>
> Beware -- you should not use OFED userspace with a non-ofed kernel for ConnectX HCAs.
> The OFED 1.4 ConnectX driver includes the XRC (Extended RC) patches -- which grab
> 23 (the MSB) of the QP number to indicate an XRC SRQ in CQEs.  Non-OFED kernels do not
> reserve bit 23 for this usage, so you will experience incompatibility problems.
>
> In general, you should not use OFED userspace libraries with non-OFED kernel distributions.

For mainstream Linux kernel development it is considered crucial to
keep the interface between user space and kernel backwards compatible.
Does the above imply that the OFED kernel components do not follow
this rule ?

Bart.