linux-kernel - Re: [PATCH rdma-next v1 2/2] RDMA/mlx5: Allow modifying Relaxed Ordering via fast registration

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Message-ID: <20210527145710.GF1002214@nvidia.com>
Date:   Thu, 27 May 2021 11:57:10 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Leon Romanovsky <leon@...nel.org>,
        Doug Ledford <dledford@...hat.com>,
        Avihai Horon <avihaih@...dia.com>,
        linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org
Subject: Re: [PATCH rdma-next v1 2/2] RDMA/mlx5: Allow modifying Relaxed
 Ordering via fast registration

On Thu, May 27, 2021 at 12:09:13PM +0100, Christoph Hellwig wrote:
>  1) qp_access_flags as a bitmask of possible operations on the queue pair
>     The way I understood the queue pairs this should really be just bits
>     for remote read, remote write and atomics, but a few places also
>     mess with memory windows and local write, which seems to be some
>     sort of iWarp cludge

Honestly I'm not completely sure what the QP access flags are for
anymore, will have to go look at some point.

>  2) IB_UVERBS_ACCESS_*.  These just get checked using ib_check_mr_access
>     and then passed into ->reg_user_mr, ->rereg_user_mr and
>     ->reg_user_mr_dmabuf

Yes. Using the kernerl flags for those user marked APIs is intended to
simplify the drivers as the user/kernel MR logic should have shared
elements

>  3) in-kernel FRWR uses IB_ACCESS_*, but all users seem to hardcode it
>     to IB_ACCESS_LOCAL_WRITE | IB_ACCESS_REMOTE_READ |
>     IB_ACCESS_REMOTE_WRITE anyway

So when a ULP is processing a READ it doesn't create a FRWR with
read-only rights? Isn't that security wrong?

Jason