Re: [bug report]concurrent blktests nvme-rdma execution lead kernel null pointer

[Leon Romanovsky <leon@kernel.org>]

On Fri, Dec 03, 2021 at 11:27:22AM +0000, Bernard Metzler wrote:
> -----"Yi Zhang" <yi.zhang@redhat.com> wrote: -----
> 
> >To: "RDMA mailing list" <linux-rdma@vger.kernel.org>
> >From: "Yi Zhang" <yi.zhang@redhat.com>
> >Date: 12/03/2021 03:20AM
> >Subject: [EXTERNAL] [bug report]concurrent blktests nvme-rdma
> >execution lead kernel null pointer
> >
> >Hello
> >With the concurrent blktests nvme-rdma execution with both rdma_rxe
> >and siw lead kernel BUG on 5.16.0-rc3, pls help check it, thanks.
> >
> 
> The RDMA core currently does not prevent us from
> assigning  both siw and rxe to the same netdev. I think this
> is what is happening here. This setting is of no sense, but
> obviously not prohibited by the RDMA infrastructure. Behavior
> is undefined and a kernel panic not unexpected. Shall we
> prevent the privileged user from doing this type of
> experiments?
> 
> A related question: should we also explicitly refuse to
> add software RDMA drivers to netdevs with RDMA hardware active?
> This is, while stupid and resulting behavior undefined, currently
> possible as well.

In old soft-RoCE manuals, I saw a request to unload mlx4_ib/mlx5_ib
modules before configuring RXE. This effectively "prevented" from
running with "RDMA hardware active". 

So I'm not surprised that it doesn't work, but why do you think that
this behavior is stupid? RXE/SIW can be seen as ULP and as such it
is ok to run many ULPs on same netdev.

Thanks