[PATCH v6 02/12] drm/xe/bo: Add purgeable bo state tracking and field madv to xe_bo

Arvind Yadav
2026-03-03T15:20:44Z

Add infrastructure for tracking purgeable state of buffer objects.
This includes:

Introduce enum xe_madv_purgeable_state with three states:
- XE_MADV_PURGEABLE_WILLNEED (0): BO is needed and should not be
purged. This is the default state for all BOs.

- XE_MADV_PURGEABLE_DONTNEED (1): BO is not currently needed and
can be purged by the kernel under memory pressure to reclaim
resources. Only non-shared BOs can be marked as DONTNEED.

- XE_MADV_PURGEABLE_PURGED (2): BO has been purged by the kernel.
Accessing a purged BO results in error. Follows i915 semantics
where once purged, the BO remains permanently invalid ("once
purged, always purged").

Add madv_purgeable field to struct xe_bo for state tracking
of purgeable state across concurrent access paths

v2:
- Add xe_bo_is_purged() helper, improve state documentation

v3:
- Add the kernel doc(Matthew Brost)
- Add the new helpers xe_bo_madv_is_dontneed(Matthew Brost)

v4:
- @madv_purgeable atomic_t → u32 change across all relevant
patches (Matt)

v5:
- Add locking documentation to madv_purgeable field comment (Matt)

Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Arvind Yadav <arvind.yadav@intel.com>
---
drivers/gpu/drm/xe/xe_bo.h | 56 ++++++++++++++++++++++++++++++++
drivers/gpu/drm/xe/xe_bo_types.h | 6 ++++
2 files changed, 62 insertions(+)

diff --git a/drivers/gpu/drm/xe/xe_bo.h b/drivers/gpu/drm/xe/xe_bo.h
index c914ab719f20..ea157d74e2fb 100644
--- a/drivers/gpu/drm/xe/xe_bo.h
+++ b/drivers/gpu/drm/xe/xe_bo.h
@@ -87,6 +87,28 @@

#define XE_PCI_BARRIER_MMAP_OFFSET (0x50 << XE_PTE_SHIFT)

+/**
+ * enum xe_madv_purgeable_state - Buffer object purgeable state enumeration
+ *
+ * This enum defines the possible purgeable states for a buffer object,
+ * allowing userspace to provide memory usage hints to the kernel for
+ * better memory management under pressure.
+ *
+ * @XE_MADV_PURGEABLE_WILLNEED: The buffer object is needed and should not be purged.
+ * This is the default state.
+ * @XE_MADV_PURGEABLE_DONTNEED: The buffer object is not currently needed and can be
+ * purged by the kernel under memory pressure.
+ * @XE_MADV_PURGEABLE_PURGED: The buffer object has been purged by the kernel.
+ *
+ * Accessing a purged buffer will result in an error. Per i915 semantics,
+ * once purged, a BO remains permanently invalid and must be destroyed and recreated.
+ */
+enum xe_madv_purgeable_state {
+ XE_MADV_PURGEABLE_WILLNEED,
+ XE_MADV_PURGEABLE_DONTNEED,
+ XE_MADV_PURGEABLE_PURGED,
+};
+
struct sg_table;

struct xe_bo *xe_bo_alloc(void);
@@ -215,6 +237,40 @@ static inline bool xe_bo_is_protected(const struct xe_bo *bo)
return bo->pxp_key_instance;
}

+/**
+ * xe_bo_is_purged() - Check if buffer object has been purged
+ * @bo: The buffer object to check
+ *
+ * Checks if the buffer object's backing store has been discarded by the
+ * kernel due to memory pressure after being marked as purgeable (DONTNEED).
+ * Once purged, the BO cannot be restored and any attempt to use it will fail.
+ *
+ * Context: Caller must hold the BO's dma-resv lock
+ * Return: true if the BO has been purged, false otherwise
+ */
+static inline bool xe_bo_is_purged(struct xe_bo *bo)
+{
+ xe_bo_assert_held(bo);
+ return bo->madv_purgeable == XE_MADV_PURGEABLE_PURGED;
+}
+
+/**
+ * xe_bo_madv_is_dontneed() - Check if BO is marked as DONTNEED
+ * @bo: The buffer object to check
+ *
+ * Checks if userspace has marked this BO as DONTNEED (i.e., its contents
+ * are not currently needed and can be discarded under memory pressure).
+ * This is used internally to decide whether a BO is eligible for purging.
+ *
+ * Context: Caller must hold the BO's dma-resv lock
+ * Return: true if the BO is marked DONTNEED, false otherwise
+ */
+static inline bool xe_bo_madv_is_dontneed(struct xe_bo *bo)
+{
+ xe_bo_assert_held(bo);
+ return bo->madv_purgeable == XE_MADV_PURGEABLE_DONTNEED;
+}
+
static inline void xe_bo_unpin_map_no_vm(struct xe_bo *bo)
{
if (likely(bo)) {
diff --git a/drivers/gpu/drm/xe/xe_bo_types.h b/drivers/gpu/drm/xe/xe_bo_types.h
index d4fe3c8dca5b..ff8317bfc1ae 100644
--- a/drivers/gpu/drm/xe/xe_bo_types.h
+++ b/drivers/gpu/drm/xe/xe_bo_types.h
@@ -108,6 +108,12 @@ struct xe_bo {
* from default
*/
u64 min_align;
+
+ /**
+ * @madv_purgeable: user space advise on BO purgeability, protected
+ * by BO's dma-resv lock.
+ */
+ u32 madv_purgeable;
};

#endif
--
2.43.0