Re: [PATCH] vfio/gvt: fix DRM_I915_GVT dependency on VFIO_MDEV

[Jason Gunthorpe]

On Thu, Apr 22, 2021 at 03:35:33PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@xxxxxxxx>
> 
> The Kconfig dependency is incomplete since DRM_I915_GVT is a 'bool'
> symbol that depends on the 'tristate' VFIO_MDEV. This allows a
> configuration with VFIO_MDEV=m, DRM_I915_GVT=y and DRM_I915=y that
> causes a link failure:
> 
> x86_64-linux-ld: drivers/gpu/drm/i915/gvt/gvt.o: in function `available_instances_show':
> gvt.c:(.text+0x67a): undefined reference to `mtype_get_parent_dev'
> x86_64-linux-ld: gvt.c:(.text+0x6a5): undefined reference to `mtype_get_type_group_id'
> x86_64-linux-ld: drivers/gpu/drm/i915/gvt/gvt.o: in function `description_show':
> gvt.c:(.text+0x76e): undefined reference to `mtype_get_parent_dev'
> x86_64-linux-ld: gvt.c:(.text+0x799): undefined reference to `mtype_get_type_group_id'
> 
> Clarify the dependency by specifically disallowing the broken
> configuration. If VFIO_MDEV is built-in, it will work, but if
> VFIO_MDEV=m, the i915 driver cannot be built-in here.
> 
> Fixes: 07e543f4f9d1 ("vfio/gvt: Make DRM_I915_GVT depend on VFIO_MDEV")
> Fixes: 9169cff168ff ("vfio/mdev: Correct the function signatures for the mdev_type_attributes")
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
>  drivers/gpu/drm/i915/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Oh kconfig stuff like this makes my head hurt, thanks for finding it

I also can't see an alternative to this ugly thing, besides having the
i915 guys properly modularize this code someday

Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>

Jason