[RFC v2 9/9] drm/xe: Add support for querying purgeable BO states

[Arvind Yadav <arvind.yadav@intel.com>]

Add support for querying purgeable buffer object states through the
XE_VM_QUERY_MEM_RANGE_ATTRS ioctl. This allows userspace to determine
the current purgeable state of BO:
  - WILLNEED (0): BO actively needed, has backing store
  - DONTNEED (1): BO eligible for purging, still valid
  - PURGED (2): BO purged by kernel, backing store freed

v2:
  - Initialize purge_state_val for non-BO VMAs to avoid leaking kernel data.

Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Signed-off-by: Arvind Yadav <arvind.yadav@intel.com>
---
 drivers/gpu/drm/xe/xe_vm.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
index cc946bff9607..fd0550d901c6 100644
--- a/drivers/gpu/drm/xe/xe_vm.c
+++ b/drivers/gpu/drm/xe/xe_vm.c
@@ -2023,6 +2023,7 @@ static int get_mem_attrs(struct xe_vm *vm, u32 *num_vmas, u64 start,
 
 	drm_gpuvm_for_each_va_range(gpuva, &vm->gpuvm, start, end) {
 		struct xe_vma *vma = gpuva_to_vma(gpuva);
+		struct xe_bo *bo;
 
 		if (i == *num_vmas)
 			return -ENOSPC;
@@ -2035,6 +2036,12 @@ static int get_mem_attrs(struct xe_vm *vm, u32 *num_vmas, u64 start,
 		attrs[i].preferred_mem_loc.migration_policy =
 		vma->attr.preferred_loc.migration_policy;
 
+		bo = xe_vma_bo(vma);
+		if (bo)
+			attrs[i].purge_state_val.val = atomic_read(&bo->madv_purgeable);
+		else /* Non-BO VMAs (userptr, null) have no purgeable state */
+			attrs[i].purge_state_val.val = DRM_XE_VMA_PURGEABLE_STATE_WILLNEED;
+
 		i++;
 	}
 
-- 
2.43.0