Re: [PATCH i-g-t v3 1/8] drm-uapi/xe_drm: Add UAPI support for purgeable buffer objects

Kamil Konieczny
2026-02-18T11:22:43Z

Hi Arvind,
On 2026-02-17 at 08:04:12 +0530, Arvind Yadav wrote:
> From: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
>
> Extend the DRM_XE_MADVISE ioctl to support purgeable buffer object
> management by adding DRM_XE_VMA_ATTR_PURGEABLE_STATE attribute type.
>
> This allows userspace applications to provide memory usage hints to
> the kernel for better memory management under pressure:
>
> This allows userspace applications to provide memory usage hints to
> the kernel for better memory management under pressure:
>
> - WILLNEED: Buffer is needed and should not be purged. If the BO was
> previously purged, retained field returns 0 indicating backing store
> was lost (once purged, always purged semantics matching i915).
>
> - DONTNEED: Buffer is not currently needed and may be purged by the
> kernel under memory pressure to free resources. Only applies to
> non-shared BOs.
>
> The implementation includes a 'retained' output field (matching i915's
> drm_i915_gem_madvise.retained) that indicates whether the BO's backing
> store still exists (1) or has been purged (0).
>
> v2:
> - Update UAPI documentation to clarify retained must be initialized
> to 0(Thomas)

This should be a sync with a kernel commit from drm-next,
see git log.

Regards,
Kamil

>
> Cc: Nishit Sharma <nishit.sharma@intel.com>
> Cc: Pravalika Gurram <pravalika.gurram@intel.com>
> 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/drm-uapi/xe_drm.h | 44 +++++++++++++++++++++++++++++++++++++++
> 1 file changed, 44 insertions(+)
>
> diff --git a/include/drm-uapi/xe_drm.h b/include/drm-uapi/xe_drm.h
> index 077e66a68..3dd1ba875 100644
> --- a/include/drm-uapi/xe_drm.h
> +++ b/include/drm-uapi/xe_drm.h
> @@ -2099,6 +2099,7 @@ struct drm_xe_madvise {
> #define DRM_XE_MEM_RANGE_ATTR_PREFERRED_LOC 0
> #define DRM_XE_MEM_RANGE_ATTR_ATOMIC 1
> #define DRM_XE_MEM_RANGE_ATTR_PAT 2
> +#define DRM_XE_VMA_ATTR_PURGEABLE_STATE 3
> /** @type: type of attribute */
> __u32 type;
>
> @@ -2189,6 +2190,49 @@ struct drm_xe_madvise {
> /** @pat_index.reserved: Reserved */
> __u64 reserved;
> } pat_index;
> +
> + /**
> + * @purge_state_val: Purgeable state configuration
> + *
> + * Used when @type == DRM_XE_VMA_ATTR_PURGEABLE_STATE.
> + *
> + * Configures the purgeable state of buffer objects in the specified
> + * virtual address range. This allows applications to hint to the kernel
> + * about bo's usage patterns for better memory management.
> + *
> + * Supported values for @purge_state_val.val:
> + * - DRM_XE_VMA_PURGEABLE_STATE_WILLNEED (0): Marks BO as needed.
> + * If BO was purged, returns retained=0 (backing store lost).
> + *
> + * - 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.
> + */
> + struct {
> +#define DRM_XE_VMA_PURGEABLE_STATE_WILLNEED 0
> +#define DRM_XE_VMA_PURGEABLE_STATE_DONTNEED 1
> + /** @purge_state_val.val: value for DRM_XE_VMA_ATTR_PURGEABLE_STATE */
> + __u32 val;
> +
> + /* @purge_state_val.pad */
> + __u32 pad;
> + /**
> + * @purge_state_val.retained: Pointer to output field for backing
> + * store status.
> + *
> + * Userspace must initialize this u32 field to 0 before the
> + * ioctl. Kernel writes to it after the operation:
> + * - 1 if backing store exists (not purged)
> + * - 0 if backing store was purged
> + *
> + * If userspace fails to initialize to 0, ioctl returns -EINVAL.
> + * This ensures a safe default (0 = assume purged) if kernel
> + * cannot write the result.
> + *
> + * Similar to i915's drm_i915_gem_madvise.retained field.
> + */
> + __u64 retained;
> + } purge_state_val;
> };
>
> /** @reserved: Reserved */
> --
> 2.43.0
>