Re: [PATCH] drm/gpuvm: Do not prepare NULL objects

["Danilo Krummrich" <dakr@kernel.org>]

(Cc: Alice)

On Fri Jan 30, 2026 at 8:19 PM CET, Jonathan Cavitt wrote:
> Statis analysis issue:
>
> drm_gpuvm_prepare_range issues an exec_object_prepare call to all
> drm_gem_objects mapped between addr and addr + range.  However, it is
> possible (albeit very unlikely) that the objects found through

It is not as unlikely as you might think. The documentation of
drm_gpuvm_for_each_va_range() explicitly states:

	"This iterator does not skip over the &drm_gpuvm's @kernel_alloc_node."

And the kernel_alloc_node does not have a GEM object set. Also, drivers are free
to insert VAs that do not have a GEM object set, e.g. when they have the
DRM_GPUVA_SPARSE flag set.

> drm_gpuvm_for_each_va_range (as connected to va->gem) are NULL, as seen
> in other functions such as drm_gpuva_link and drm_gpuva_unlink_defer.

That said, there is a "real" justification, other than "we do the same thing in
other functions" that would have been good to put this into the commit message.

The reason I say "would have been" is because this patch has already been
applied -- unfortunately without going through the corresponding maintainer (and
non-Intel reviewers). I only noticed it by accident as I saw it pop up in
drm-misc-next.

No action needed as the code itself is obviously correct, but for the next time,
please make sure to send patches to the corresponding maintainers and reviewers.

- Danilo