drm/xe/vm: Validate userptr during gpu vma prefetching

If a userptr vma subject to prefetching was already invalidated
or invalidated during the prefetch operation, the operation would
repeatedly return -EAGAIN which would typically cause an infinite
loop.

Validate the userptr to ensure this doesn't happen.

v2:
- Don't fallthrough from UNMAP to PREFETCH (Matthew Brost)

Fixes: 5bd24e7 ("drm/xe/vm: Subclass userptr vmas")
Fixes: 617eebb ("drm/xe: Fix array of binds")
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: <stable@vger.kernel.org> # v6.9+
Suggested-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250228073058.59510-2-thomas.hellstrom@linux.intel.com
(cherry picked from commit 03c346d)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

Author: Thomas Hellström

drivers/gpu/drm/xe/xe_vm.c

@@ -2286,8 +2286,17 @@ static int vm_bind_ioctl_ops_parse(struct xe_vm *vm, struct drm_gpuva_ops *ops,
 			break;
 		}
 		case DRM_GPUVA_OP_UNMAP:
+			xe_vma_ops_incr_pt_update_ops(vops, op->tile_mask);
+			break;
 		case DRM_GPUVA_OP_PREFETCH:
-			/* FIXME: Need to skip some prefetch ops */
+			vma = gpuva_to_vma(op->base.prefetch.va);
+
+			if (xe_vma_is_userptr(vma)) {
+				err = xe_vma_userptr_pin_pages(to_userptr_vma(vma));
+				if (err)
+					return err;
+			}
+
 			xe_vma_ops_incr_pt_update_ops(vops, op->tile_mask);
 			break;
 		default: