Re: [PATCH 0/6] drm: reject empty TTM range manager sizes

[Christian König]

On 10/19/26 10:41, Jiale Yao wrote:
> drm_mm_init() rejects a zero-length allocation range with a BUG check.
> Several DRM TTM users can derive a zero page count from device-provided
> VRAM metadata and pass it to the range manager.

The BUG check is there to point out driver bugs which try to initialize a VRAM manager while no VRAM is installed.

That is intended behavior and returning an error instead of running into a BUG() makes that intended behavior go away and eventually cause more problems down the road.

So absolutely clear NAK to that.

Regards,
Christian.

> 
> This series rejects empty ranges at the affected callers and adds a
> defensive check in the common range manager. Patches 1 through 4 and
> 6 validate the individual driver inputs. Patch 5 protects the shared
> range-manager API against any remaining zero-page caller.
> 
> The series was checked with scripts/checkpatch.pl for every code patch.
> 
> Jiale Yao (6):
>   drm/vram-helper: reject empty VRAM ranges
>   drm/nouveau: reject empty VRAM ranges
>   drm/qxl: reject empty TTM memory ranges
>   drm/radeon: reject empty VRAM ranges
>   drm/ttm: reject empty range manager sizes
>   drm/vmwgfx: reject empty VRAM ranges
> 
>  drivers/gpu/drm/drm_gem_vram_helper.c   | 3 +++
>  drivers/gpu/drm/nouveau/nouveau_ttm.c   | 3 +++
>  drivers/gpu/drm/qxl/qxl_ttm.c           | 3 +++
>  drivers/gpu/drm/radeon/radeon_ttm.c     | 3 +++
>  drivers/gpu/drm/ttm/ttm_range_manager.c | 3 +++
>  drivers/gpu/drm/vmwgfx/vmwgfx_drv.c     | 4 ++++
>  6 files changed, 19 insertions(+)
>