Re: [PATCH v4 08/10] vfio: selftests: Add mlx5 driver - HW init and command interface

[David Matlack <dmatlack@google.com>]

On 2026-08-12 11:59 AM, Jason Gunthorpe wrote:

> diff --git a/tools/testing/selftests/vfio/lib/drivers/mlx5/mlx5_hw.h b/tools/testing/selftests/vfio/lib/drivers/mlx5/mlx5_hw.h
> new file mode 100644
> index 00000000000000..a2506ec8a19523
> --- /dev/null
> +++ b/tools/testing/selftests/vfio/lib/drivers/mlx5/mlx5_hw.h
> @@ -0,0 +1,108 @@
> +/* SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB */
> +/*
> + * mlx5 VFIO selftest driver - HW definitions
> + *
> + * Typed wrappers, constants, and helpers for programming mlx5 hardware
> + * via the VFIO selftest framework.  Most HW constants and all MLX5_SET/GET
> + * macros come from the kernel headers (mlx5_ifc.h, mlx5_ifc_macros.h).
> + */
> +#ifndef SELFTESTS_VFIO_MLX5_HW_H
> +#define SELFTESTS_VFIO_MLX5_HW_H
> +
> +#include <linux/io.h>
> +#include <linux/build_bug.h>
> +#include <vdso/bits.h>
> +
> +#include "mlx5_ifc.h"
> +#include "mlx5_ifc_macros.h"

I'm getting a compiler warning here when building with clang which is
getting upgraded to error from -Werror.

  /usr/local/google/home/dmatlack/kernel/trees/review/tools/testing/selftests/vfio/lib/drivers/mlx5/mlx5_ifc.h:2706:50: error: field 'menu'
  with variable sized type 'struct mlx5_ifc_resource_dump_menu_segment_bits' not at the end of a struct or class is a GNU
        extension [-Werror,-Wgnu-variable-sized-type-not-at-end]
         2706 |         struct mlx5_ifc_resource_dump_menu_segment_bits menu;
               |                                                         ^
           1 error generated.
           make: *** [lib/libvfio.mk:36:

I assume the mlx5 header needs to be fixed... But we can also work
around it in VFIO selftests if that turns out to be a can of worms:

diff --git a/tools/testing/selftests/vfio/lib/drivers/mlx5/mlx5_hw.h b/tools/testing/selftests/vfio/lib/drivers/mlx5/mlx5_hw.h
index 2c451e411ec1..b9fad2b722a0 100644
--- a/tools/testing/selftests/vfio/lib/drivers/mlx5/mlx5_hw.h
+++ b/tools/testing/selftests/vfio/lib/drivers/mlx5/mlx5_hw.h
@@ -13,9 +13,18 @@
 #include <linux/build_bug.h>
 #include <vdso/bits.h>

+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wgnu-variable-sized-type-not-at-end"
+#endif
+
 #include "mlx5_ifc.h"
 #include "mlx5_ifc_macros.h"

+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif
+
 /*
  * Typed HW object wrappers for driver region arrays.
  *