Since gen4 systems are really new this also sounds like a new feature to me.. You need to be concerned that changing the pci setup doesn't cause regressions on existing systems too.
We have covered this with all of our types of cards and servers (gen3 and gen4).
Perhaps the description should say:
IB/hfi1: Insure full Gen3 speed in a Gen4 system
And maybe explain what the actual user visible impact is here. Sounds like plugging a card into a gen4 system will not run at gen3 speeds?
Ok. I will reissue the patch some changes in the commit message.
Mike