[RFC v3 5/8] drm/xe/vm: Prevent binding of purged buffer objects

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

Add check_purged parameter to vma_lock_and_validate() to block
new mapping operations on purged BOs while allowing cleanup
operations to proceed.

Purged BOs have their backing pages freed by the kernel. New
mapping operations (MAP, PREFETCH, REMAP) must be rejected with
-EINVAL to prevent GPU access to invalid memory. Cleanup
operations (UNMAP) must be allowed so applications can release
resources after detecting purge via the retained field.

REMAP operations require mixed handling - reject new prev/next
VMAs if the BO is purged, but allow the unmap portion to proceed
for cleanup.

The check_purged parameter distinguishes between these cases:
true for new mappings (must reject), false for cleanup (allow).

v2:
  - Clarify that purged BOs are permanently invalid (i915 semantics)
  - Remove incorrect claim about madvise(WILLNEED) restoring purged BOs

v3:
  - Move xe_bo_is_purged check under vma_lock_and_validate (Matthew Brost)
  - Add check_purged parameter to distinguish new mappings from cleanup
  - Allow UNMAP operations to prevent resource leaks
  - Handle REMAP operation's dual nature (cleanup + new mappings)

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 | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
index 762098d368a6..9a6c9a26c6da 100644
--- a/drivers/gpu/drm/xe/xe_vm.c
+++ b/drivers/gpu/drm/xe/xe_vm.c
@@ -2864,7 +2864,7 @@ static void vm_bind_ioctl_ops_unwind(struct xe_vm *vm,
 }
 
 static int vma_lock_and_validate(struct drm_exec *exec, struct xe_vma *vma,
-				 bool res_evict, bool validate)
+				 bool res_evict, bool validate, bool check_purged)
 {
 	struct xe_bo *bo = xe_vma_bo(vma);
 	struct xe_vm *vm = xe_vma_vm(vma);
@@ -2873,6 +2873,11 @@ static int vma_lock_and_validate(struct drm_exec *exec, struct xe_vma *vma,
 	if (bo) {
 		if (!bo->vm)
 			err = drm_exec_lock_obj(exec, &bo->ttm.base);
+
+		/* Reject new mappings to purged BOs; allow cleanup operations */
+		if (!err && check_purged && xe_bo_is_purged(bo))
+			err = -EINVAL;
+
 		if (!err && validate)
 			err = xe_bo_validate(bo, vm,
 					     !xe_vm_in_preempt_fence_mode(vm) &&
@@ -2964,7 +2969,8 @@ static int op_lock_and_prep(struct drm_exec *exec, struct xe_vm *vm,
 			err = vma_lock_and_validate(exec, op->map.vma,
 						    res_evict,
 						    !xe_vm_in_fault_mode(vm) ||
-						    op->map.immediate);
+						    op->map.immediate,
+						    true);
 		break;
 	case DRM_GPUVA_OP_REMAP:
 		err = check_ufence(gpuva_to_vma(op->base.remap.unmap->va));
@@ -2973,13 +2979,13 @@ static int op_lock_and_prep(struct drm_exec *exec, struct xe_vm *vm,
 
 		err = vma_lock_and_validate(exec,
 					    gpuva_to_vma(op->base.remap.unmap->va),
-					    res_evict, false);
+					    res_evict, false, false);
 		if (!err && op->remap.prev)
 			err = vma_lock_and_validate(exec, op->remap.prev,
-						    res_evict, true);
+						    res_evict, true, true);
 		if (!err && op->remap.next)
 			err = vma_lock_and_validate(exec, op->remap.next,
-						    res_evict, true);
+						    res_evict, true, true);
 		break;
 	case DRM_GPUVA_OP_UNMAP:
 		err = check_ufence(gpuva_to_vma(op->base.unmap.va));
@@ -2988,7 +2994,7 @@ static int op_lock_and_prep(struct drm_exec *exec, struct xe_vm *vm,
 
 		err = vma_lock_and_validate(exec,
 					    gpuva_to_vma(op->base.unmap.va),
-					    res_evict, false);
+					    res_evict, false, false);
 		break;
 	case DRM_GPUVA_OP_PREFETCH:
 	{
@@ -3003,7 +3009,7 @@ static int op_lock_and_prep(struct drm_exec *exec, struct xe_vm *vm,
 
 		err = vma_lock_and_validate(exec,
 					    gpuva_to_vma(op->base.prefetch.va),
-					    res_evict, false);
+					    res_evict, false, true);
 		if (!err && !xe_vma_has_no_bo(vma))
 			err = xe_bo_migrate(xe_vma_bo(vma),
 					    region_to_mem_type[region],
-- 
2.43.0