cxl/port: Move dport tracking to an xarray

Reduce the complexity and the overhead of walking the topology to
determine endpoint connectivity to root decoder interleave
configurations.

Note that cxl_detach_ep(), after it determines that the last @ep has
departed and decides to delete the port, now needs to walk the dport
array with the device_lock() held to remove entries. Previously
list_splice_init() could be used atomically delete all dport entries at
once and then perform entry tear down outside the lock. There is no
list_splice_init() equivalent for the xarray.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/165784331647.1758207.6345820282285119339.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
index 960a77864f337f3f8eecd9d6d37f585446341852..96346c6be0219790183f9c2905ac2f5d055f94c3 100644 (file)
--- a/drivers/cxl/core/hdm.c
+++ b/drivers/cxl/core/hdm.c
@@ -50,8 +50,9 @@ static int add_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld,
 int devm_cxl_add_passthrough_decoder(struct cxl_port *port)
 {
        struct cxl_switch_decoder *cxlsd;
-       struct cxl_dport *dport;
+       struct cxl_dport *dport = NULL;
        int single_port_map[1];
+       unsigned long index;
 
        cxlsd = cxl_switch_decoder_alloc(port, 1);
        if (IS_ERR(cxlsd))
@@ -59,7 +60,8 @@ int devm_cxl_add_passthrough_decoder(struct cxl_port *port)
 
        device_lock_assert(&port->dev);
 
-       dport = list_first_entry(&port->dports, typeof(*dport), list);
+       xa_for_each(&port->dports, index, dport)
+               break;
        single_port_map[0] = dport->port_id;
 
        return add_hdm_decoder(port, &cxlsd->cxld, single_port_map);

diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index 63d76aa582d3189f8eb41a22efab191607caf0da..c7f1844d58deb4fd176fc5717f89ea4fcd53b4d0 100644 (file)
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -452,6 +452,7 @@ static void cxl_port_release(struct device *dev)
        xa_for_each(&port->endpoints, index, ep)
                cxl_ep_remove(port, ep);
        xa_destroy(&port->endpoints);
+       xa_destroy(&port->dports);
        ida_free(&cxl_port_ida, port->id);
        kfree(port);
 }
@@ -581,7 +582,7 @@ static struct cxl_port *cxl_port_alloc(struct device *uport,
        port->component_reg_phys = component_reg_phys;
        ida_init(&port->decoder_ida);
        port->hdm_end = -1;
-       INIT_LIST_HEAD(&port->dports);
+       xa_init(&port->dports);
        xa_init(&port->endpoints);
 
        device_initialize(dev);
@@ -711,17 +712,13 @@ static int match_root_child(struct device *dev, const void *match)
                return 0;
 
        port = to_cxl_port(dev);
-       device_lock(dev);
-       list_for_each_entry(dport, &port->dports, list) {
-               iter = match;
-               while (iter) {
-                       if (iter == dport->dport)
-                               goto out;
-                       iter = iter->parent;
-               }
+       iter = match;
+       while (iter) {
+               dport = cxl_find_dport_by_dev(port, iter);
+               if (dport)
+                       break;
+               iter = iter->parent;
        }
-out:
-       device_unlock(dev);
 
        return !!iter;
 }
@@ -745,9 +742,10 @@ EXPORT_SYMBOL_NS_GPL(find_cxl_root, CXL);
 static struct cxl_dport *find_dport(struct cxl_port *port, int id)
 {
        struct cxl_dport *dport;
+       unsigned long index;
 
        device_lock_assert(&port->dev);
-       list_for_each_entry (dport, &port->dports, list)
+       xa_for_each(&port->dports, index, dport)
                if (dport->port_id == id)
                        return dport;
        return NULL;
@@ -759,15 +757,15 @@ static int add_dport(struct cxl_port *port, struct cxl_dport *new)
 
        device_lock_assert(&port->dev);
        dup = find_dport(port, new->port_id);
-       if (dup)
+       if (dup) {
                dev_err(&port->dev,
                        "unable to add dport%d-%s non-unique port id (%s)\n",
                        new->port_id, dev_name(new->dport),
                        dev_name(dup->dport));
-       else
-               list_add_tail(&new->list, &port->dports);
-
-       return dup ? -EEXIST : 0;
+               return -EBUSY;
+       }
+       return xa_insert(&port->dports, (unsigned long)new->dport, new,
+                        GFP_KERNEL);
 }
 
 /*
@@ -794,10 +792,8 @@ static void cxl_dport_remove(void *data)
        struct cxl_dport *dport = data;
        struct cxl_port *port = dport->port;
 
+       xa_erase(&port->dports, (unsigned long) dport->dport);
        put_device(dport->dport);
-       cond_cxl_root_lock(port);
-       list_del(&dport->list);
-       cond_cxl_root_unlock(port);
 }
 
 static void cxl_dport_unlink(void *data)
@@ -849,7 +845,6 @@ struct cxl_dport *devm_cxl_add_dport(struct cxl_port *port,
        if (!dport)
                return ERR_PTR(-ENOMEM);
 
-       INIT_LIST_HEAD(&dport->list);
        dport->dport = dport_dev;
        dport->port_id = port_id;
        dport->component_reg_phys = component_reg_phys;
@@ -1040,19 +1035,27 @@ EXPORT_SYMBOL_NS_GPL(cxl_endpoint_autoremove, CXL);
  * for a port to be unregistered is when all memdevs beneath that port have gone
  * through ->remove(). This "bottom-up" removal selectively removes individual
  * child ports manually. This depends on devm_cxl_add_port() to not change is
- * devm action registration order.
+ * devm action registration order, and for dports to have already been
+ * destroyed by reap_dports().
  */
-static void delete_switch_port(struct cxl_port *port, struct list_head *dports)
+static void delete_switch_port(struct cxl_port *port)
+{
+       devm_release_action(port->dev.parent, cxl_unlink_uport, port);
+       devm_release_action(port->dev.parent, unregister_port, port);
+}
+
+static void reap_dports(struct cxl_port *port)
 {
-       struct cxl_dport *dport, *_d;
+       struct cxl_dport *dport;
+       unsigned long index;
 
-       list_for_each_entry_safe(dport, _d, dports, list) {
+       device_lock_assert(&port->dev);
+
+       xa_for_each(&port->dports, index, dport) {
                devm_release_action(&port->dev, cxl_dport_unlink, dport);
                devm_release_action(&port->dev, cxl_dport_remove, dport);
                devm_kfree(&port->dev, dport);
        }
-       devm_release_action(port->dev.parent, cxl_unlink_uport, port);
-       devm_release_action(port->dev.parent, unregister_port, port);
 }
 
 static struct cxl_ep *cxl_ep_load(struct cxl_port *port,
@@ -1069,8 +1072,8 @@ static void cxl_detach_ep(void *data)
        for (iter = &cxlmd->dev; iter; iter = grandparent(iter)) {
                struct device *dport_dev = grandparent(iter);
                struct cxl_port *port, *parent_port;
-               LIST_HEAD(reap_dports);
                struct cxl_ep *ep;
+               bool died = false;
 
                if (!dport_dev)
                        break;
@@ -1110,15 +1113,16 @@ static void cxl_detach_ep(void *data)
                         * enumerated port. Block new cxl_add_ep() and garbage
                         * collect the port.
                         */
+                       died = true;
                        port->dead = true;
-                       list_splice_init(&port->dports, &reap_dports);
+                       reap_dports(port);
                }
                device_unlock(&port->dev);
 
-               if (!list_empty(&reap_dports)) {
+               if (died) {
                        dev_dbg(&cxlmd->dev, "delete %s\n",
                                dev_name(&port->dev));
-                       delete_switch_port(port, &reap_dports);
+                       delete_switch_port(port);
                }
                put_device(&port->dev);
                device_unlock(&parent_port->dev);
@@ -1297,23 +1301,6 @@ struct cxl_port *cxl_mem_find_port(struct cxl_memdev *cxlmd,
 }
 EXPORT_SYMBOL_NS_GPL(cxl_mem_find_port, CXL);
 
-struct cxl_dport *cxl_find_dport_by_dev(struct cxl_port *port,
-                                       const struct device *dev)
-{
-       struct cxl_dport *dport;
-
-       device_lock(&port->dev);
-       list_for_each_entry(dport, &port->dports, list)
-               if (dport->dport == dev) {
-                       device_unlock(&port->dev);
-                       return dport;
-               }
-
-       device_unlock(&port->dev);
-       return NULL;
-}
-EXPORT_SYMBOL_NS_GPL(cxl_find_dport_by_dev, CXL);
-
 static int decoder_populate_targets(struct cxl_switch_decoder *cxlsd,
                                    struct cxl_port *port, int *target_map)
 {
@@ -1324,7 +1311,7 @@ static int decoder_populate_targets(struct cxl_switch_decoder *cxlsd,
 
        device_lock_assert(&port->dev);
 
-       if (list_empty(&port->dports))
+       if (xa_empty(&port->dports))
                return -EINVAL;
 
        write_seqlock(&cxlsd->target_lock);

diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index f1dd60c86e2a69eb6171b82adcfb709760198cd9..ac950fb45dd2caaa43b6bafd549083a848a24f28 100644 (file)
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -346,7 +346,7 @@ struct cxl_port {
        struct device *uport;
        struct device *host_bridge;
        int id;
-       struct list_head dports;
+       struct xarray dports;
        struct xarray endpoints;
        struct cxl_dport *parent_dport;
        struct ida decoder_ida;
@@ -361,20 +361,24 @@ struct cxl_port {
        bool cdat_available;
 };
 
+static inline struct cxl_dport *
+cxl_find_dport_by_dev(struct cxl_port *port, const struct device *dport_dev)
+{
+       return xa_load(&port->dports, (unsigned long)dport_dev);
+}
+
 /**
  * struct cxl_dport - CXL downstream port
  * @dport: PCI bridge or firmware device representing the downstream link
  * @port_id: unique hardware identifier for dport in decoder target list
  * @component_reg_phys: downstream port component registers
  * @port: reference to cxl_port that contains this downstream port
- * @list: node for a cxl_port's list of cxl_dport instances
  */
 struct cxl_dport {
        struct device *dport;
        int port_id;
        resource_size_t component_reg_phys;
        struct cxl_port *port;
-       struct list_head list;
 };
 
 /**
@@ -417,8 +421,6 @@ bool schedule_cxl_memdev_detach(struct cxl_memdev *cxlmd);
 struct cxl_dport *devm_cxl_add_dport(struct cxl_port *port,
                                     struct device *dport, int port_id,
                                     resource_size_t component_reg_phys);
-struct cxl_dport *cxl_find_dport_by_dev(struct cxl_port *port,
-                                       const struct device *dev);
 
 struct cxl_decoder *to_cxl_decoder(struct device *dev);
 struct cxl_root_decoder *to_cxl_root_decoder(struct device *dev);