On Thu, Oct 18, 2012 at 4:58 PM, Roland Dreier <rol...@kernel.org> wrote: > > On Wed, Oct 17, 2012 at 9:42 AM, Or Gerlitz <ogerl...@mellanox.com> wrote: > > > > Also, a respin of the 64B CQE/EQE patches (kernel and user-space), over > > the V1 posting > > you were asking for max flexibility - e.g expose/force update of guests > > only if needed > > and similarily for libmlx4, I think I have this now, would love feedback > > though. > > > > I tested this with both modified/non-modified mlx4 guest drivers, and > > with > > both modified/non-modified libmlx4. The only pain point I was hitting, > > if non modified libmlx4 on systems with CX3 and modified kernel, on > > the V1 discussion Roland -- you made a comment we might need a module > > param > > here to provide admins a way to let systems with old libmlx4 to work > > with fresh kernels?! > > So I don't think this change (which changes the kernel ABI) is appropriate > for 3.7 after the merge window in any case. > > With that said I think we need a stronger compatibility story even for > 3.8. > Suppose I'm running a virtualized system with SR-IOV, and I have a stable > guest that is working perfectly. Then I want to update the hypervisor to > a newer kernel to get more KVM features or something. > > If that kernel update enables 64B CQEs, then my guest is now broken. > And I don't want to force a guest update just to get a new hypervisor. > > So I think we need some flag passed to the mlx4_core (that drives the > PPF) that lets the user opt into 64B CQEs. I would suggest that we > start with the default value be "disabled" and then flip that after a few > kernel versions (and print something in the kernel log when we detect > 64B-CQE-capable HW when we're running with 64B CQEs disabled). > > Unfortunately because the 64B CQE setting is global for the whole > adapter (instead of being per-CQ), I don't see any better way to > support old userspace/guest kernels.
OK, let it be, will resubmit with that flag, Or. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
