Re: [Intel-xe] [PATCH v2 02/14] drm/xe/uapi: Separate bo_create placement from flags

["Welty, Brian" <brian.welty@intel.com>]

On 11/22/2023 6:38 AM, Francois Dugast wrote:
> From: Rodrigo Vivi <rodrigo.vivi@intel.com>
> 
> Although the flags are about the creation, the memory placement
> of the BO deserves a proper dedicated field in the uapi.
> 
> Besides getting more clear, it also allows to remove the
> 'magic' shifts from the flags that was a concern during the
> uapi reviews.
> 
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Signed-off-by: Francois Dugast <francois.dugast@intel.com>
> Reviewed-by: Matthew Brost <matthew.brost@intel.com>
> ---
>   drivers/gpu/drm/xe/xe_bo.c | 15 +++++++--------
>   include/uapi/drm/xe_drm.h  | 12 ++++++------
>   2 files changed, 13 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
> index 4305f5cbc2ab..bbce4cd80f7e 100644
> --- a/drivers/gpu/drm/xe/xe_bo.c
> +++ b/drivers/gpu/drm/xe/xe_bo.c
> @@ -1799,19 +1799,18 @@ int xe_gem_create_ioctl(struct drm_device *dev, void *data,
>   	u32 handle;
>   	int err;
>   
> -	if (XE_IOCTL_DBG(xe, args->extensions) || XE_IOCTL_DBG(xe, args->pad) ||
> +	if (XE_IOCTL_DBG(xe, args->extensions) ||
>   	    XE_IOCTL_DBG(xe, args->reserved[0] || args->reserved[1]))
>   		return -EINVAL;
>   
> +	/* at least one valid memory placement must be specified */
> +	if (XE_IOCTL_DBG(xe, !(args->placement & xe->info.mem_region_mask)))
> +		return -EINVAL;

I think you are missing to test that args->placement is *only* a mask of 
regions.   Looks like you allow other bits to be included and those will
get slammed into bo_flags below.

Probably:

   if (XE_IOCTL_DBG(xe, (args->placement & ~xe->info.mem_region_mask) || 
!args->placement))
      return -EINVAL;


-Brian


> +
>   	if (XE_IOCTL_DBG(xe, args->flags &
>   			 ~(DRM_XE_GEM_CREATE_FLAG_DEFER_BACKING |
>   			   DRM_XE_GEM_CREATE_FLAG_SCANOUT |
> -			   DRM_XE_GEM_CREATE_FLAG_NEEDS_VISIBLE_VRAM |
> -			   xe->info.mem_region_mask)))
> -		return -EINVAL;
> -
> -	/* at least one memory type must be specified */
> -	if (XE_IOCTL_DBG(xe, !(args->flags & xe->info.mem_region_mask)))
> +			   DRM_XE_GEM_CREATE_FLAG_NEEDS_VISIBLE_VRAM)))
>   		return -EINVAL;
>   
>   	if (XE_IOCTL_DBG(xe, args->handle))
> @@ -1832,7 +1831,7 @@ int xe_gem_create_ioctl(struct drm_device *dev, void *data,
>   	if (args->flags & DRM_XE_GEM_CREATE_FLAG_SCANOUT)
>   		bo_flags |= XE_BO_SCANOUT_BIT;
>   
> -	bo_flags |= args->flags << (ffs(XE_BO_CREATE_SYSTEM_BIT) - 1);
> +	bo_flags |= args->placement << (ffs(XE_BO_CREATE_SYSTEM_BIT) - 1);
>   
>   	if (args->flags & DRM_XE_GEM_CREATE_FLAG_NEEDS_VISIBLE_VRAM) {
>   		if (XE_IOCTL_DBG(xe, !(bo_flags & XE_BO_CREATE_VRAM_MASK)))
> diff --git a/include/uapi/drm/xe_drm.h b/include/uapi/drm/xe_drm.h
> index b0d13bc6d9cf..1bdd20d3c4a8 100644
> --- a/include/uapi/drm/xe_drm.h
> +++ b/include/uapi/drm/xe_drm.h
> @@ -500,8 +500,11 @@ struct drm_xe_gem_create {
>   	 */
>   	__u64 size;
>   
> -#define DRM_XE_GEM_CREATE_FLAG_DEFER_BACKING		(0x1 << 24)
> -#define DRM_XE_GEM_CREATE_FLAG_SCANOUT			(0x1 << 25)
> +	/** @placement: A mask of memory instances of where BO can be placed. */
> +	__u32 placement;
> +
> +#define DRM_XE_GEM_CREATE_FLAG_DEFER_BACKING		(1 << 0)
> +#define DRM_XE_GEM_CREATE_FLAG_SCANOUT			(1 << 1)
>   /*
>    * When using VRAM as a possible placement, ensure that the corresponding VRAM
>    * allocation will always use the CPU accessible part of VRAM. This is important
> @@ -517,7 +520,7 @@ struct drm_xe_gem_create {
>    * display surfaces, therefore the kernel requires setting this flag for such
>    * objects, otherwise an error is thrown on small-bar systems.
>    */
> -#define DRM_XE_GEM_CREATE_FLAG_NEEDS_VISIBLE_VRAM	(0x1 << 26)
> +#define DRM_XE_GEM_CREATE_FLAG_NEEDS_VISIBLE_VRAM	(1 << 2)
>   	/**
>   	 * @flags: Flags, currently a mask of memory instances of where BO can
>   	 * be placed
> @@ -541,9 +544,6 @@ struct drm_xe_gem_create {
>   	 */
>   	__u32 handle;
>   
> -	/** @pad: MBZ */
> -	__u32 pad;
> -
>   	/** @reserved: Reserved */
>   	__u64 reserved[2];
>   };