Re: [PATCH v8 2/3] vfio/ism: Implement vfio_pci driver for ISM devices

Jason Gunthorpe
2026-03-30T15:56:54Z

On Mon, Mar 30, 2026 at 09:36:46AM -0600, Alex Williamson wrote:
> There's risk involved with changing the default shift. The fear is
> there's userspace drivers that hard code the shift. DPDK was even such
> a user at one point, iirc. Maybe it's ok to break such users, maybe
> there are actually no such users left and it's all FUD at this point.
> Either way, I have a hard time justifying that risk for a single,
> obscure S390 device.

If we go ahead with that DMABUF series could obscure cases like this
be told to just get a DMABUF FD and then mmap it? Avoid this whole
issue?

Jason