drm/amdkfd: Cleanup IO links during KFD device removal

Currently, the IO-links to the device being removed from topology,
are not cleared. As a result, there would be dangling links left in
the KFD topology. This patch aims to fix the following:
1. Cleanup all IO links to the device being removed.
2. Ensure that node numbering in sysfs and nodes proximity domain
   values are consistent after the device is removed:
   a. Adding a device and removing a GPU device are made mutually
      exclusive.
   b. The global proximity domain counter is no longer required to be
      an atomic counter. A normal 32-bit counter can be used instead.
3. Update generation_count to let user-mode know that topology has
   changed due to device removal.

CC: Shuotao Xu <shuotaoxu@microsoft.com>
Reviewed-by: Shuotao Xu <shuotaoxu@microsoft.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Mukul Joshi <mukul.joshi@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdkfd/kfd_crat.c

@@ -1056,7 +1056,7 @@ static int kfd_parse_subtype_iolink(struct crat_subtype_iolink *iolink,
 	 * table, add corresponded reversed direction link now.
 	 */
 	if (props && (iolink->flags & CRAT_IOLINK_FLAGS_BI_DIRECTIONAL)) {
-		to_dev = kfd_topology_device_by_proximity_domain(id_to);
+		to_dev = kfd_topology_device_by_proximity_domain_no_lock(id_to);
 		if (!to_dev)
 			return -ENODEV;
 		/* same everything but the other direction */
@@ -2225,7 +2225,7 @@ static int kfd_create_vcrat_image_gpu(void *pcrat_image,
 	 */
 	if (kdev->hive_id) {
 		for (nid = 0; nid < proximity_domain; ++nid) {
-			peer_dev = kfd_topology_device_by_proximity_domain(nid);
+			peer_dev = kfd_topology_device_by_proximity_domain_no_lock(nid);
 			if (!peer_dev->gpu)
 				continue;
 			if (peer_dev->gpu->hive_id != kdev->hive_id)

drivers/gpu/drm/amd/amdkfd/kfd_priv.h

@@ -1016,6 +1016,8 @@ int kfd_topology_add_device(struct kfd_dev *gpu);
 int kfd_topology_remove_device(struct kfd_dev *gpu);
 struct kfd_topology_device *kfd_topology_device_by_proximity_domain(
 						uint32_t proximity_domain);
+struct kfd_topology_device *kfd_topology_device_by_proximity_domain_no_lock(
+						uint32_t proximity_domain);
 struct kfd_topology_device *kfd_topology_device_by_id(uint32_t gpu_id);
 struct kfd_dev *kfd_device_by_id(uint32_t gpu_id);
 struct kfd_dev *kfd_device_by_pci_dev(const struct pci_dev *pdev);

drivers/gpu/drm/amd/amdkfd/kfd_topology.c

@@ -46,22 +46,32 @@ static struct list_head topology_device_list;
 static struct kfd_system_properties sys_props;
 
 static DECLARE_RWSEM(topology_lock);
-static atomic_t topology_crat_proximity_domain;
+static uint32_t topology_crat_proximity_domain;
 
-struct kfd_topology_device *kfd_topology_device_by_proximity_domain(
+struct kfd_topology_device *kfd_topology_device_by_proximity_domain_no_lock(
 						uint32_t proximity_domain)
 {
 	struct kfd_topology_device *top_dev;
 	struct kfd_topology_device *device = NULL;
 
-	down_read(&topology_lock);
-
 	list_for_each_entry(top_dev, &topology_device_list, list)
 		if (top_dev->proximity_domain == proximity_domain) {
 			device = top_dev;
 			break;
 		}
 
+	return device;
+}
+
+struct kfd_topology_device *kfd_topology_device_by_proximity_domain(
+						uint32_t proximity_domain)
+{
+	struct kfd_topology_device *device = NULL;
+
+	down_read(&topology_lock);
+
+	device = kfd_topology_device_by_proximity_domain_no_lock(
+							proximity_domain);
 	up_read(&topology_lock);
 
 	return device;
@@ -1060,7 +1070,7 @@ int kfd_topology_init(void)
 	down_write(&topology_lock);
 	kfd_topology_update_device_list(&temp_topology_device_list,
 					&topology_device_list);
-	atomic_set(&topology_crat_proximity_domain, sys_props.num_devices-1);
+	topology_crat_proximity_domain = sys_props.num_devices-1;
 	ret = kfd_topology_update_sysfs();
 	up_write(&topology_lock);
 
@@ -1295,8 +1305,6 @@ int kfd_topology_add_device(struct kfd_dev *gpu)
 
 	pr_debug("Adding new GPU (ID: 0x%x) to topology\n", gpu_id);
 
-	proximity_domain = atomic_inc_return(&topology_crat_proximity_domain);
-
 	/* Include the CPU in xGMI hive if xGMI connected by assigning it the hive ID. */
 	if (gpu->hive_id && gpu->adev->gmc.xgmi.connected_to_cpu) {
 		struct kfd_topology_device *top_dev;
@@ -1321,12 +1329,16 @@ int kfd_topology_add_device(struct kfd_dev *gpu)
 	 */
 	dev = kfd_assign_gpu(gpu);
 	if (!dev) {
+		down_write(&topology_lock);
+		proximity_domain = ++topology_crat_proximity_domain;
+
 		res = kfd_create_crat_image_virtual(&crat_image, &image_size,
 						    COMPUTE_UNIT_GPU, gpu,
 						    proximity_domain);
 		if (res) {
 			pr_err("Error creating VCRAT for GPU (ID: 0x%x)\n",
 			       gpu_id);
+			topology_crat_proximity_domain--;
 			return res;
 		}
 		res = kfd_parse_crat_table(crat_image,
@@ -1335,10 +1347,10 @@ int kfd_topology_add_device(struct kfd_dev *gpu)
 		if (res) {
 			pr_err("Error parsing VCRAT for GPU (ID: 0x%x)\n",
 			       gpu_id);
+			topology_crat_proximity_domain--;
 			goto err;
 		}
 
-		down_write(&topology_lock);
 		kfd_topology_update_device_list(&temp_topology_device_list,
 			&topology_device_list);
 
@@ -1485,25 +1497,78 @@ int kfd_topology_add_device(struct kfd_dev *gpu)
 	return res;
 }
 
+/**
+ * kfd_topology_update_io_links() - Update IO links after device removal.
+ * @proximity_domain: Proximity domain value of the dev being removed.
+ *
+ * The topology list currently is arranged in increasing order of
+ * proximity domain.
+ *
+ * Two things need to be done when a device is removed:
+ * 1. All the IO links to this device need to be removed.
+ * 2. All nodes after the current device node need to move
+ *    up once this device node is removed from the topology
+ *    list. As a result, the proximity domain values for
+ *    all nodes after the node being deleted reduce by 1.
+ *    This would also cause the proximity domain values for
+ *    io links to be updated based on new proximity domain
+ *    values.
+ *
+ * Context: The caller must hold write topology_lock.
+ */
+static void kfd_topology_update_io_links(int proximity_domain)
+{
+	struct kfd_topology_device *dev;
+	struct kfd_iolink_properties *iolink, *tmp;
+
+	list_for_each_entry(dev, &topology_device_list, list) {
+		if (dev->proximity_domain > proximity_domain)
+			dev->proximity_domain--;
+
+		list_for_each_entry_safe(iolink, tmp, &dev->io_link_props, list) {
+			/*
+			 * If there is an io link to the dev being deleted
+			 * then remove that IO link also.
+			 */
+			if (iolink->node_to == proximity_domain) {
+				list_del(&iolink->list);
+				dev->io_link_count--;
+				dev->node_props.io_links_count--;
+			} else if (iolink->node_from > proximity_domain) {
+				iolink->node_from--;
+			} else if (iolink->node_to > proximity_domain) {
+				iolink->node_to--;
+			}
+		}
+
+	}
+}
+
 int kfd_topology_remove_device(struct kfd_dev *gpu)
 {
 	struct kfd_topology_device *dev, *tmp;
 	uint32_t gpu_id;
 	int res = -ENODEV;
+	int i = 0;
 
 	down_write(&topology_lock);
 
-	list_for_each_entry_safe(dev, tmp, &topology_device_list, list)
+	list_for_each_entry_safe(dev, tmp, &topology_device_list, list) {
 		if (dev->gpu == gpu) {
 			gpu_id = dev->gpu_id;
 			kfd_remove_sysfs_node_entry(dev);
 			kfd_release_topology_device(dev);
 			sys_props.num_devices--;
+			kfd_topology_update_io_links(i);
+			topology_crat_proximity_domain = sys_props.num_devices-1;
+			sys_props.generation_count++;
 			res = 0;
 			if (kfd_topology_update_sysfs() < 0)
 				kfd_topology_release_sysfs();
 			break;
 		}
+		i++;
+	}
 
 	up_write(&topology_lock);