Re: [PATCH rdma-next 00/10] Enable relaxed ordering for ULPs

[Tom Talpey]

On 4/12/2021 6:48 PM, Jason Gunthorpe wrote:
> On Mon, Apr 12, 2021 at 04:20:47PM -0400, Tom Talpey wrote:
>
> > So the issue is only in testing all the providers and platforms,
> > to be sure this new behavior isn't tickling anything that went
> > unnoticed all along, because no RDMA provider ever issued RO.
>
> The mlx5 ethernet driver has run in RO mode for a long time, and it
> operates in basically the same way as RDMA. The issues with Haswell
> have been worked out there already.
>
> The only open question is if the ULPs have errors in their
> implementation, which I don't think we can find out until we apply
> this series and people start running their tests aggressively.

I agree that the core RO support should go in. But turning it on
by default for a ULP should be the decision of each ULP maintainer.
It's a huge risk to shift all the storage drivers overnight. How
do you propose to ensure the aggressive testing happens?

One thing that worries me is the patch02 on-by-default for the dma_lkey.
There's no way for a ULP to prevent IB_ACCESS_RELAXED_ORDERING
from being set in __ib_alloc_pd().

Tom.