Re: [PATCH v3 23/25] drm/xe: Compute dumb-buffer sizes with drm_mode_size_dumb()

[Matthew Auld <matthew.auld@xxxxxxxxx>]

On 18/02/2025 14:23, Thomas Zimmermann wrote:
> Call drm_mode_size_dumb() to compute dumb-buffer scanline pitch
> and buffer size. Align the pitch to a multiple of 8. Align the
> buffer size according to hardware requirements.
>
> Xe's internal calculation allowed for 64-bit wide buffer sizes, but
> the ioctl's internal checks always verified against 32-bit wide limits.
> Hance, it is safe to limit the driver code to 32-bit calculations as
> well.
>
> v3:
> - mention 32-bit calculation in commit description (Matthew)
>
> Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
> Cc: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
> Cc: "Thomas Hellström" <thomas.hellstrom@xxxxxxxxxxxxxxx>
> Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
Reviewed-by: Matthew Auld <matthew.auld@xxxxxxxxx>


> ---
>   drivers/gpu/drm/xe/xe_bo.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
> index 78d09c5ed26d..b34f446ad57d 100644
> --- a/drivers/gpu/drm/xe/xe_bo.c
> +++ b/drivers/gpu/drm/xe/xe_bo.c
> @@ -9,6 +9,7 @@
>   #include <linux/nospec.h>
>   
>   #include <drm/drm_drv.h>
> +#include <drm/drm_dumb_buffers.h>
>   #include <drm/drm_gem_ttm_helper.h>
>   #include <drm/drm_managed.h>
>   #include <drm/ttm/ttm_device.h>
> @@ -2672,14 +2673,13 @@ int xe_bo_dumb_create(struct drm_file *file_priv,
>         struct xe_device *xe = to_xe_device(dev);
>         struct xe_bo *bo;
>         uint32_t handle;
> -       int cpp = DIV_ROUND_UP(args->bpp, 8);
>         int err;
>         u32 page_size = max_t(u32, PAGE_SIZE,
>                 xe->info.vram_flags & XE_VRAM_FLAGS_NEED64K ? SZ_64K : SZ_4K);
>   
> -	args->pitch = ALIGN(args->width * cpp, 64);
> -       args->size = ALIGN(mul_u32_u32(args->pitch, args->height),
> -                          page_size);
> +       err = drm_mode_size_dumb(dev, args, SZ_64, page_size);
> +       if (err)
> +               return err;
>   
>   	bo = xe_bo_create_user(xe, NULL, NULL, args->size,
>                                DRM_XE_GEM_CPU_CACHING_WC,