drm/xe: Update PT layer with better error handling

Update PT layer so if a memory allocation for a PTE fails the error can
be propagated to the user without requiring the VM to be killed.

v5:
 - change return value invalidation_fence_init to void (Matthew Auld)
v7:
 - Invert i,j usage in two places (Matthew Auld)
 - s/0/NULL (Matthew Auld)
 - Don't ignore return value of xe_pt_new_shared (Matthew Auld)
 - Don't check for NULL in xe_pt_entry (Matthew Auld)
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240704041652.272920-7-matthew.brost@intel.com

drivers/gpu/drm/xe/xe_pt.c

@@ -846,19 +846,27 @@ xe_vm_populate_pgtable(struct xe_migrate_pt_update *pt_update, struct xe_tile *t
 	}
 }
 
-static void xe_pt_abort_bind(struct xe_vma *vma,
-			     struct xe_vm_pgtable_update *entries,
-			     u32 num_entries)
+static void xe_pt_cancel_bind(struct xe_vma *vma,
+			      struct xe_vm_pgtable_update *entries,
+			      u32 num_entries)
 {
 	u32 i, j;
 
 	for (i = 0; i < num_entries; i++) {
-		if (!entries[i].pt_entries)
+		struct xe_pt *pt = entries[i].pt;
+
+		if (!pt)
 			continue;
 
-		for (j = 0; j < entries[i].qwords; j++)
-			xe_pt_destroy(entries[i].pt_entries[j].pt, xe_vma_vm(vma)->flags, NULL);
+		if (pt->level) {
+			for (j = 0; j < entries[i].qwords; j++)
+				xe_pt_destroy(entries[i].pt_entries[j].pt,
+					      xe_vma_vm(vma)->flags, NULL);
+		}
+
 		kfree(entries[i].pt_entries);
+		entries[i].pt_entries = NULL;
+		entries[i].qwords = 0;
 	}
 }
 
@@ -874,10 +882,61 @@ static void xe_pt_commit_locks_assert(struct xe_vma *vma)
 	xe_vm_assert_held(vm);
 }
 
-static void xe_pt_commit_bind(struct xe_vma *vma,
-			      struct xe_vm_pgtable_update *entries,
-			      u32 num_entries, bool rebind,
-			      struct llist_head *deferred)
+static void xe_pt_commit(struct xe_vma *vma,
+			 struct xe_vm_pgtable_update *entries,
+			 u32 num_entries, struct llist_head *deferred)
+{
+	u32 i, j;
+
+	xe_pt_commit_locks_assert(vma);
+
+	for (i = 0; i < num_entries; i++) {
+		struct xe_pt *pt = entries[i].pt;
+
+		if (!pt->level)
+			continue;
+
+		for (j = 0; j < entries[i].qwords; j++) {
+			struct xe_pt *oldpte = entries[i].pt_entries[j].pt;
+
+			xe_pt_destroy(oldpte, xe_vma_vm(vma)->flags, deferred);
+		}
+	}
+}
+
+static void xe_pt_abort_bind(struct xe_vma *vma,
+			     struct xe_vm_pgtable_update *entries,
+			     u32 num_entries, bool rebind)
+{
+	int i, j;
+
+	xe_pt_commit_locks_assert(vma);
+
+	for (i = num_entries - 1; i >= 0; --i) {
+		struct xe_pt *pt = entries[i].pt;
+		struct xe_pt_dir *pt_dir;
+
+		if (!rebind)
+			pt->num_live -= entries[i].qwords;
+
+		if (!pt->level)
+			continue;
+
+		pt_dir = as_xe_pt_dir(pt);
+		for (j = 0; j < entries[i].qwords; j++) {
+			u32 j_ = j + entries[i].ofs;
+			struct xe_pt *newpte = xe_pt_entry(pt_dir, j_);
+			struct xe_pt *oldpte = entries[i].pt_entries[j].pt;
+
+			pt_dir->children[j_] = oldpte ? &oldpte->base : 0;
+			xe_pt_destroy(newpte, xe_vma_vm(vma)->flags, NULL);
+		}
+	}
+}
+
+static void xe_pt_commit_prepare_bind(struct xe_vma *vma,
+				      struct xe_vm_pgtable_update *entries,
+				      u32 num_entries, bool rebind)
 {
 	u32 i, j;
 
@@ -897,12 +956,13 @@ static void xe_pt_commit_bind(struct xe_vma *vma,
 		for (j = 0; j < entries[i].qwords; j++) {
 			u32 j_ = j + entries[i].ofs;
 			struct xe_pt *newpte = entries[i].pt_entries[j].pt;
+			struct xe_pt *oldpte = NULL;
 
 			if (xe_pt_entry(pt_dir, j_))
-				xe_pt_destroy(xe_pt_entry(pt_dir, j_),
-					      xe_vma_vm(vma)->flags, deferred);
+				oldpte = xe_pt_entry(pt_dir, j_);
 
 			pt_dir->children[j_] = &newpte->base;
+			entries[i].pt_entries[j].pt = oldpte;
 		}
 	}
 }
@@ -926,8 +986,6 @@ xe_pt_prepare_bind(struct xe_tile *tile, struct xe_vma *vma,
 	err = xe_pt_stage_bind(tile, vma, entries, num_entries);
 	if (!err)
 		xe_tile_assert(tile, *num_entries);
-	else /* abort! */
-		xe_pt_abort_bind(vma, entries, *num_entries);
 
 	return err;
 }
@@ -1305,10 +1363,10 @@ static void invalidation_fence_work_func(struct work_struct *w)
 				     ifence->end, ifence->asid);
 }
 
-static int invalidation_fence_init(struct xe_gt *gt,
-				   struct invalidation_fence *ifence,
-				   struct dma_fence *fence,
-				   u64 start, u64 end, u32 asid)
+static void invalidation_fence_init(struct xe_gt *gt,
+				    struct invalidation_fence *ifence,
+				    struct dma_fence *fence,
+				    u64 start, u64 end, u32 asid)
 {
 	int ret;
 
@@ -1340,8 +1398,6 @@ static int invalidation_fence_init(struct xe_gt *gt,
 	}
 
 	xe_gt_assert(gt, !ret || ret == -ENOENT);
-
-	return ret && ret != -ENOENT ? ret : 0;
 }
 
 struct xe_pt_stage_unbind_walk {
@@ -1426,6 +1482,7 @@ xe_pt_stage_unbind_post_descend(struct xe_ptw *parent, pgoff_t offset,
 	struct xe_pt *xe_child = container_of(*child, typeof(*xe_child), base);
 	pgoff_t end_offset;
 	u64 size = 1ull << walk->shifts[--level];
+	int err;
 
 	if (!IS_ALIGNED(addr, size))
 		addr = xe_walk->modified_start;
@@ -1441,7 +1498,10 @@ xe_pt_stage_unbind_post_descend(struct xe_ptw *parent, pgoff_t offset,
 				     &end_offset))
 		return 0;
 
-	(void)xe_pt_new_shared(&xe_walk->wupd, xe_child, offset, false);
+	err = xe_pt_new_shared(&xe_walk->wupd, xe_child, offset, true);
+	if (err)
+		return err;
+
 	xe_walk->wupd.updates[level].update->qwords = end_offset - offset;
 
 	return 0;
@@ -1509,32 +1569,54 @@ xe_migrate_clear_pgtable_callback(struct xe_migrate_pt_update *pt_update,
 		memset64(ptr, empty, num_qwords);
 }
 
+static void xe_pt_abort_unbind(struct xe_vma *vma,
+			       struct xe_vm_pgtable_update *entries,
+			       u32 num_entries)
+{
+	int i, j;
+
+	xe_pt_commit_locks_assert(vma);
+
+	for (i = num_entries - 1; i >= 0; --i) {
+		struct xe_vm_pgtable_update *entry = &entries[i];
+		struct xe_pt *pt = entry->pt;
+		struct xe_pt_dir *pt_dir = as_xe_pt_dir(pt);
+
+		pt->num_live += entry->qwords;
+
+		if (!pt->level)
+			continue;
+
+		for (j = entry->ofs; j < entry->ofs + entry->qwords; j++)
+			pt_dir->children[i] =
+				entries[i].pt_entries[j - entry->ofs].pt ?
+				&entries[i].pt_entries[j - entry->ofs].pt->base : NULL;
+	}
+}
+
 static void
-xe_pt_commit_unbind(struct xe_vma *vma,
-		    struct xe_vm_pgtable_update *entries, u32 num_entries,
-		    struct llist_head *deferred)
+xe_pt_commit_prepare_unbind(struct xe_vma *vma,
+			    struct xe_vm_pgtable_update *entries,
+			    u32 num_entries)
 {
-	u32 j;
+	int i, j;
 
 	xe_pt_commit_locks_assert(vma);
 
-	for (j = 0; j < num_entries; ++j) {
-		struct xe_vm_pgtable_update *entry = &entries[j];
+	for (i = 0; i < num_entries; ++i) {
+		struct xe_vm_pgtable_update *entry = &entries[i];
 		struct xe_pt *pt = entry->pt;
+		struct xe_pt_dir *pt_dir;
 
 		pt->num_live -= entry->qwords;
-		if (pt->level) {
-			struct xe_pt_dir *pt_dir = as_xe_pt_dir(pt);
-			u32 i;
-
-			for (i = entry->ofs; i < entry->ofs + entry->qwords;
-			     i++) {
-				if (xe_pt_entry(pt_dir, i))
-					xe_pt_destroy(xe_pt_entry(pt_dir, i),
-						      xe_vma_vm(vma)->flags, deferred);
+		if (!pt->level)
+			continue;
 
-				pt_dir->children[i] = NULL;
-			}
+		pt_dir = as_xe_pt_dir(pt);
+		for (j = entry->ofs; j < entry->ofs + entry->qwords; j++) {
+			entry->pt_entries[j - entry->ofs].pt =
+				xe_pt_entry(pt_dir, j);
+			pt_dir->children[j] = NULL;
 		}
 	}
 }
@@ -1580,7 +1662,6 @@ static int bind_op_prepare(struct xe_vm *vm, struct xe_tile *tile,
 {
 	u32 current_op = pt_update_ops->current_op;
 	struct xe_vm_pgtable_update_op *pt_op = &pt_update_ops->ops[current_op];
-	struct llist_head *deferred = &pt_update_ops->deferred;
 	int err;
 
 	xe_bo_assert_held(xe_vma_bo(vma));
@@ -1628,11 +1709,12 @@ static int bind_op_prepare(struct xe_vm *vm, struct xe_tile *tile,
 			/* We bump also if batch_invalidate_tlb is true */
 			vm->tlb_flush_seqno++;
 
-		/* FIXME: Don't commit right away */
 		vma->tile_staged |= BIT(tile->id);
 		pt_op->vma = vma;
-		xe_pt_commit_bind(vma, pt_op->entries, pt_op->num_entries,
-				  pt_op->rebind, deferred);
+		xe_pt_commit_prepare_bind(vma, pt_op->entries,
+					  pt_op->num_entries, pt_op->rebind);
+	} else {
+		xe_pt_cancel_bind(vma, pt_op->entries, pt_op->num_entries);
 	}
 
 	return err;
@@ -1644,7 +1726,6 @@ static int unbind_op_prepare(struct xe_tile *tile,
 {
 	u32 current_op = pt_update_ops->current_op;
 	struct xe_vm_pgtable_update_op *pt_op = &pt_update_ops->ops[current_op];
-	struct llist_head *deferred = &pt_update_ops->deferred;
 	int err;
 
 	if (!((vma->tile_present | vma->tile_staged) & BIT(tile->id)))
@@ -1680,9 +1761,7 @@ static int unbind_op_prepare(struct xe_tile *tile,
 	pt_update_ops->needs_userptr_lock |= xe_vma_is_userptr(vma);
 	pt_update_ops->needs_invalidation = true;
 
-	/* FIXME: Don't commit right away */
-	xe_pt_commit_unbind(vma, pt_op->entries, pt_op->num_entries,
-			    deferred);
+	xe_pt_commit_prepare_unbind(vma, pt_op->entries, pt_op->num_entries);
 
 	return 0;
 }
@@ -1903,7 +1982,7 @@ xe_pt_update_ops_run(struct xe_tile *tile, struct xe_vma_ops *vops)
 	struct invalidation_fence *ifence = NULL;
 	struct xe_range_fence *rfence;
 	struct xe_vma_op *op;
-	int err = 0;
+	int err = 0, i;
 	struct xe_migrate_pt_update update = {
 		.ops = pt_update_ops->needs_userptr_lock ?
 			&userptr_migrate_ops :
@@ -1923,8 +2002,10 @@ xe_pt_update_ops_run(struct xe_tile *tile, struct xe_vma_ops *vops)
 
 	if (pt_update_ops->needs_invalidation) {
 		ifence = kzalloc(sizeof(*ifence), GFP_KERNEL);
-		if (!ifence)
-			return ERR_PTR(-ENOMEM);
+		if (!ifence) {
+			err = -ENOMEM;
+			goto kill_vm_tile1;
+		}
 	}
 
 	rfence = kzalloc(sizeof(*rfence), GFP_KERNEL);
@@ -1939,6 +2020,15 @@ xe_pt_update_ops_run(struct xe_tile *tile, struct xe_vma_ops *vops)
 		goto free_rfence;
 	}
 
+	/* Point of no return - VM killed if failure after this */
+	for (i = 0; i < pt_update_ops->current_op; ++i) {
+		struct xe_vm_pgtable_update_op *pt_op = &pt_update_ops->ops[i];
+
+		xe_pt_commit(pt_op->vma, pt_op->entries,
+			     pt_op->num_entries, &pt_update_ops->deferred);
+		pt_op->vma = NULL;	/* skip in xe_pt_update_ops_abort */
+	}
+
 	if (xe_range_fence_insert(&vm->rftree[tile->id], rfence,
 				  &xe_range_fence_kfree_ops,
 				  pt_update_ops->start,
@@ -1947,12 +2037,9 @@ xe_pt_update_ops_run(struct xe_tile *tile, struct xe_vma_ops *vops)
 
 	/* tlb invalidation must be done before signaling rebind */
 	if (ifence) {
-		err = invalidation_fence_init(tile->primary_gt, ifence, fence,
-					      pt_update_ops->start,
-					      pt_update_ops->last,
-					      vm->usm.asid);
-		if (err)
-			goto put_fence;
+		invalidation_fence_init(tile->primary_gt, ifence, fence,
+					pt_update_ops->start,
+					pt_update_ops->last, vm->usm.asid);
 		fence = &ifence->base.base;
 	}
 
@@ -1969,14 +2056,13 @@ xe_pt_update_ops_run(struct xe_tile *tile, struct xe_vma_ops *vops)
 
 	return fence;
 
-put_fence:
-	if (pt_update_ops->needs_userptr_lock)
-		up_read(&vm->userptr.notifier_lock);
-	dma_fence_put(fence);
 free_rfence:
 	kfree(rfence);
 free_ifence:
 	kfree(ifence);
+kill_vm_tile1:
+	if (err != -EAGAIN && tile->id)
+		xe_vm_kill(vops->vm, false);
 
 	return ERR_PTR(err);
 }
@@ -1997,12 +2083,10 @@ void xe_pt_update_ops_fini(struct xe_tile *tile, struct xe_vma_ops *vops)
 	lockdep_assert_held(&vops->vm->lock);
 	xe_vm_assert_held(vops->vm);
 
-	/* FIXME: Not 100% correct */
-	for (i = 0; i < pt_update_ops->num_ops; ++i) {
+	for (i = 0; i < pt_update_ops->current_op; ++i) {
 		struct xe_vm_pgtable_update_op *pt_op = &pt_update_ops->ops[i];
 
-		if (pt_op->bind)
-			xe_pt_free_bind(pt_op->entries, pt_op->num_entries);
+		xe_pt_free_bind(pt_op->entries, pt_op->num_entries);
 	}
 	xe_bo_put_commit(&vops->pt_update_ops[tile->id].deferred);
 }
@@ -2016,10 +2100,28 @@ void xe_pt_update_ops_fini(struct xe_tile *tile, struct xe_vma_ops *vops)
  */
 void xe_pt_update_ops_abort(struct xe_tile *tile, struct xe_vma_ops *vops)
 {
+	struct xe_vm_pgtable_update_ops *pt_update_ops =
+		&vops->pt_update_ops[tile->id];
+	int i;
+
 	lockdep_assert_held(&vops->vm->lock);
 	xe_vm_assert_held(vops->vm);
 
-	/* FIXME: Just kill VM for now + cleanup PTs */
+	for (i = pt_update_ops->num_ops - 1; i >= 0; --i) {
+		struct xe_vm_pgtable_update_op *pt_op =
+			&pt_update_ops->ops[i];
+
+		if (!pt_op->vma || i >= pt_update_ops->current_op)
+			continue;
+
+		if (pt_op->bind)
+			xe_pt_abort_bind(pt_op->vma, pt_op->entries,
+					 pt_op->num_entries,
+					 pt_op->rebind);
+		else
+			xe_pt_abort_unbind(pt_op->vma, pt_op->entries,
+					   pt_op->num_entries);
+	}
+
 	xe_bo_put_commit(&vops->pt_update_ops[tile->id].deferred);
-	xe_vm_kill(vops->vm, false);
 }