Re: [RFC v2 8/9] drm/xe/uapi: Add UAPI for purgeable bo state to madvise query response

[Matthew Brost <matthew.brost@intel.com>]

On Mon, Dec 01, 2025 at 11:20:18AM +0530, Arvind Yadav wrote:
> From: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
> 
> Complete the purgeable buffer object UAPI by adding the response
> structure to drm_xe_mem_range_attr for querying current purgeable
> state of buffer objects within a memory range.
> 
> This allows userspace to determine the current state of BOs:
> - DRM_XE_VMA_PURGEABLE_STATE_WILLNEED (0): BO actively needed, has backing store
> - DRM_XE_VMA_PURGEABLE_STATE_DONTNEED (1): BO eligible for purging, still has backing
> - DRM_XE_VMA_PURGEABLE_STATE_PURGED (2): BO purged, backing store freed (read-only)
> 
> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
> Signed-off-by: Arvind Yadav <arvind.yadav@intel.com>
> ---
>  include/uapi/drm/xe_drm.h | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/include/uapi/drm/xe_drm.h b/include/uapi/drm/xe_drm.h
> index 02d63938d16f..8f289a2849ff 100644
> --- a/include/uapi/drm/xe_drm.h
> +++ b/include/uapi/drm/xe_drm.h
> @@ -2147,10 +2147,14 @@ struct drm_xe_madvise {
>  		 *  - DRM_XE_VMA_PURGEABLE_STATE_DONTNEED (1): Hints that BO is not
>  		 *    currently needed. Kernel may purge it under memory pressure.
>  		 *    Only applies to non-shared BOs. Returns retained=1 if not purged.
> +		 *
> +		 *  - DRM_XE_VMA_PURGEABLE_STATE_PURGED: Read-only state indicating
> +		 *    the BO purge state.

This is tricky one. Since the value of purgable state can immediately
change after getting populated, is there any value in reporting this to
user space? My guess is no. So with that, I'd probably remove this uAPI.

Matt

>  		 */
>  		struct {
>  #define DRM_XE_VMA_PURGEABLE_STATE_WILLNEED	0
>  #define DRM_XE_VMA_PURGEABLE_STATE_DONTNEED	1
> +#define DRM_XE_VMA_PURGEABLE_STATE_PURGED	2
>  			/** @purge_state_val.val: value for DRM_XE_VMA_ATTR_PURGEABLE_STATE */
>  			__u32 val;
>  			/**
> @@ -2224,6 +2228,15 @@ struct drm_xe_mem_range_attr {
>  		__u32 reserved;
>  	} pat_index;
>  
> +	/** @purge_state_val: Purgeable state configuration */
> +	struct {
> +		/** @purge_state_val.val: value for DRM_XE_VMA_ATTR_PURGEABLE_STATE */
> +		__u32 val;
> +
> +		/** @purge_state_val.reserved: Reserved */
> +		__u32 reserved;
> +	} purge_state_val;
> +
>  	/** @reserved: Reserved */
>  	__u64 reserved[2];
>  };
> -- 
> 2.43.0
>