Subject: Re: [PATCH 00/11] mlx5 support for VFIO self test

From: Jason Gunthorpe <[email-masked]>
Date: Fri, 1 May 2026 13:43:14 -0300

On Fri, May 01, 2026 at 09:11:11AM -0700, David Matlack wrote:
> On Thu, Apr 30, 2026 at 5:08 PM Jason Gunthorpe <[email-masked]> wrote:
> >
> > Add an mlx5 driver to VFIO self test. This is largely a remix of the
> > existing VFIO mlx5 driver in rdma-core. It uses an RDMA loopback QP
> > to issue RDMA WRITE operations which effectively perform memory
> > copies using DMA. Since mlx5 has a stable programming ABI this
> > should work on devices from CX5 to current HW. The device FW must
> > support the QP loopback configuration.
> 
> > This entire series was coded by Claude Code in about 4 days.
> 
> Very exciting. Josh Hilke from Google is also working on using AI to
> create a selftest driver for Intel IGB NICs so VFIO selftests can run
> in QEMU [1]. So it's encouraging to see you were able to do it with
> mlx5.
> 
> [1] https://www.qemu.org/docs/master/system/devices/igb.html

Yes! I would feed DPDK in as well in this case? Combined with the
kernel driver it should be doable. It is much easier if you understand
how the NIC works, of course. This worked out significantly because I
guided it through sufficiently small steps and knew where to find all
the quality reference material..

> >  - Make it work on a PF too (this is surprisingly hard!).
> 
> Can it work on CX VFs? We're interested in continuously performing
> memory copies across a Live Update using a VF via selftests to
> demonstrate SR-IOV preservation (when we eventually get there).

Yes, I started with VF because it is simpler. The PF support flow
requires a bunch more complicated stuff.

Jason