drm/xe: Rework eviction rejection of bound external bos

For preempt_fence mode VM's we're rejecting eviction of
shared bos during VM_BIND. However, since we do this in the
move() callback, we're getting an eviction failure warning from
TTM. The TTM callback intended for these things is
eviction_valuable().

However, the latter doesn't pass in the struct ttm_operation_ctx
needed to determine whether the caller needs this.

Instead, attach the needed information to the vm under the
vm->resv, until we've been able to update TTM to provide the
needed information. And add sufficient lockdep checks to prevent
misuse and races.

v2:
- Fix a copy-paste error in xe_vm_clear_validating()
v3:
- Fix kerneldoc errors.

Signed-off-by: Thomas Hellström <[email protected]>
Fixes: 0af944f ("drm/xe: Reject BO eviction if BO is bound to current VM")
Reviewed-by: Matthew Brost <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
(cherry picked from commit 9d55586)
Signed-off-by: Thomas Hellström <[email protected]>

Author: Thomas Hellström

drivers/gpu/drm/xe/xe_bo.c

@@ -841,21 +841,6 @@ static int xe_bo_move(struct ttm_buffer_object *ttm_bo, bool evict,
 		goto out;
 	}
 
-	/* Reject BO eviction if BO is bound to current VM. */
-	if (evict && ctx->resv) {
-		struct drm_gpuvm_bo *vm_bo;
-
-		drm_gem_for_each_gpuvm_bo(vm_bo, &bo->ttm.base) {
-			struct xe_vm *vm = gpuvm_to_vm(vm_bo->vm);
-
-			if (xe_vm_resv(vm) == ctx->resv &&
-			    xe_vm_in_preempt_fence_mode(vm)) {
-				ret = -EBUSY;
-				goto out;
-			}
-		}
-	}
-
 	/*
 	 * Failed multi-hop where the old_mem is still marked as
 	 * TTM_PL_FLAG_TEMPORARY, should just be a dummy move.
@@ -1013,6 +998,25 @@ static long xe_bo_shrink_purge(struct ttm_operation_ctx *ctx,
 	return lret;
 }
 
+static bool
+xe_bo_eviction_valuable(struct ttm_buffer_object *bo, const struct ttm_place *place)
+{
+	struct drm_gpuvm_bo *vm_bo;
+
+	if (!ttm_bo_eviction_valuable(bo, place))
+		return false;
+
+	if (!xe_bo_is_xe_bo(bo))
+		return true;
+
+	drm_gem_for_each_gpuvm_bo(vm_bo, &bo->base) {
+		if (xe_vm_is_validating(gpuvm_to_vm(vm_bo->vm)))
+			return false;
+	}
+
+	return true;
+}
+
 /**
  * xe_bo_shrink() - Try to shrink an xe bo.
  * @ctx: The struct ttm_operation_ctx used for shrinking.
@@ -1047,7 +1051,7 @@ long xe_bo_shrink(struct ttm_operation_ctx *ctx, struct ttm_buffer_object *bo,
 	    (flags.purge && !xe_tt->purgeable))
 		return -EBUSY;
 
-	if (!ttm_bo_eviction_valuable(bo, &place))
+	if (!xe_bo_eviction_valuable(bo, &place))
 		return -EBUSY;
 
 	if (!xe_bo_is_xe_bo(bo) || !xe_bo_get_unless_zero(xe_bo))
@@ -1588,7 +1592,7 @@ const struct ttm_device_funcs xe_ttm_funcs = {
 	.io_mem_pfn = xe_ttm_io_mem_pfn,
 	.access_memory = xe_ttm_access_memory,
 	.release_notify = xe_ttm_bo_release_notify,
-	.eviction_valuable = ttm_bo_eviction_valuable,
+	.eviction_valuable = xe_bo_eviction_valuable,
 	.delete_mem_notify = xe_ttm_bo_delete_mem_notify,
 	.swap_notify = xe_ttm_bo_swap_notify,
 };
@@ -2431,6 +2435,8 @@ int xe_bo_validate(struct xe_bo *bo, struct xe_vm *vm, bool allow_res_evict)
 		.no_wait_gpu = false,
 		.gfp_retry_mayfail = true,
 	};
+	struct pin_cookie cookie;
+	int ret;
 
 	if (vm) {
 		lockdep_assert_held(&vm->lock);
@@ -2440,8 +2446,12 @@ int xe_bo_validate(struct xe_bo *bo, struct xe_vm *vm, bool allow_res_evict)
 		ctx.resv = xe_vm_resv(vm);
 	}
 
+	cookie = xe_vm_set_validating(vm, allow_res_evict);
 	trace_xe_bo_validate(bo);
-	return ttm_bo_validate(&bo->ttm, &bo->placement, &ctx);
+	ret = ttm_bo_validate(&bo->ttm, &bo->placement, &ctx);
+	xe_vm_clear_validating(vm, allow_res_evict, cookie);
+
+	return ret;
 }
 
 bool xe_bo_is_xe_bo(struct ttm_buffer_object *bo)

drivers/gpu/drm/xe/xe_vm.h

@@ -301,6 +301,75 @@ void xe_vm_snapshot_capture_delayed(struct xe_vm_snapshot *snap);
 void xe_vm_snapshot_print(struct xe_vm_snapshot *snap, struct drm_printer *p);
 void xe_vm_snapshot_free(struct xe_vm_snapshot *snap);
 
+/**
+ * xe_vm_set_validating() - Register this task as currently making bos resident
+ * @allow_res_evict: Allow eviction of buffer objects bound to @vm when
+ * validating.
+ * @vm: Pointer to the vm or NULL.
+ *
+ * Register this task as currently making bos resident for the vm. Intended
+ * to avoid eviction by the same task of shared bos bound to the vm.
+ * Call with the vm's resv lock held.
+ *
+ * Return: A pin cookie that should be used for xe_vm_clear_validating().
+ */
+static inline struct pin_cookie xe_vm_set_validating(struct xe_vm *vm,
+						     bool allow_res_evict)
+{
+	struct pin_cookie cookie = {};
+
+	if (vm && !allow_res_evict) {
+		xe_vm_assert_held(vm);
+		cookie = lockdep_pin_lock(&xe_vm_resv(vm)->lock.base);
+		/* Pairs with READ_ONCE in xe_vm_is_validating() */
+		WRITE_ONCE(vm->validating, current);
+	}
+
+	return cookie;
+}
+
+/**
+ * xe_vm_clear_validating() - Unregister this task as currently making bos resident
+ * @vm: Pointer to the vm or NULL
+ * @allow_res_evict: Eviction from @vm was allowed. Must be set to the same
+ * value as for xe_vm_set_validation().
+ * @cookie: Cookie obtained from xe_vm_set_validating().
+ *
+ * Register this task as currently making bos resident for the vm. Intended
+ * to avoid eviction by the same task of shared bos bound to the vm.
+ * Call with the vm's resv lock held.
+ */
+static inline void xe_vm_clear_validating(struct xe_vm *vm, bool allow_res_evict,
+					  struct pin_cookie cookie)
+{
+	if (vm && !allow_res_evict) {
+		lockdep_unpin_lock(&xe_vm_resv(vm)->lock.base, cookie);
+		/* Pairs with READ_ONCE in xe_vm_is_validating() */
+		WRITE_ONCE(vm->validating, NULL);
+	}
+}
+
+/**
+ * xe_vm_is_validating() - Whether bos bound to the vm are currently being made resident
+ * by the current task.
+ * @vm: Pointer to the vm.
+ *
+ * If this function returns %true, we should be in a vm resv locked region, since
+ * the current process is the same task that called xe_vm_set_validating().
+ * The function asserts that that's indeed the case.
+ *
+ * Return: %true if the task is currently making bos resident, %false otherwise.
+ */
+static inline bool xe_vm_is_validating(struct xe_vm *vm)
+{
+	/* Pairs with WRITE_ONCE in xe_vm_is_validating() */
+	if (READ_ONCE(vm->validating) == current) {
+		xe_vm_assert_held(vm);
+		return true;
+	}
+	return false;
+}
+
 #if IS_ENABLED(CONFIG_DRM_XE_USERPTR_INVAL_INJECT)
 void xe_vma_userptr_force_invalidate(struct xe_userptr_vma *uvma);
 #else

drivers/gpu/drm/xe/xe_vm_types.h

@@ -310,6 +310,14 @@ struct xe_vm {
 	 * protected by the vm resv.
 	 */
 	u64 tlb_flush_seqno;
+	/**
+	 * @validating: The task that is currently making bos resident for this vm.
+	 * Protected by the VM's resv for writing. Opportunistic reading can be done
+	 * using READ_ONCE. Note: This is a workaround for the
+	 * TTM eviction_valuable() callback not being passed a struct
+	 * ttm_operation_context(). Future work might want to address this.
+	 */
+	struct task_struct *validating;
 	/** @batch_invalidate_tlb: Always invalidate TLB before batch start */
 	bool batch_invalidate_tlb;
 	/** @xef: XE file handle for tracking this VM's drm client */