Re: [PATCH rdma-next 1/2] arm64/io: add memcpy_toio_64

[Jason Gunthorpe <jgg@nvidia.com>]

On Fri, Nov 24, 2023 at 04:59:38PM +0100, Niklas Schnelle wrote:
 
> This should be as easy as adding
> 
> #define memcpy_toio_64(to, from) zpci_memcpy_toio(to, from, 64)
> 
> to arch/s390/include/asm/io.h. I'm wondering if we should do that as
> part of this series. It's not as good as a special case but probably
> better than the existing loop.

Makes sense

> I don't think we have any existing in-kernel users of memcpy_toio() on
> s390 so far though so I'd like to give this some extra testing. Could
> you share instructions on how to exercise the code path of patch 2 on a
> ConnectX-5 or 6? Is this exercised e.g. when using NVMe-oF RDMA?

Simply boot and look at pr_debug from mlx5 to see if writecombining is
on or off - you want to see on.

Thanks,
Jason