net/virtio-net: Convert to hotplug state machine

Install the callbacks via the state machine.

The driver supports multiple instances and therefore the new
cpuhp_state_add_instance_nocalls() infrastrucure is used. The driver
currently uses get_online_cpus() to avoid missing a CPU hotplug event while
invoking virtnet_set_affinity(). This could be avoided by using
cpuhp_state_add_instance() variant which holds the hotplug lock and invokes
callback during registration. This is more or less a 1:1 conversion of the
current code.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: netdev@vger.kernel.org
Cc: Will Deacon <will.deacon@arm.com>
Cc: virtualization@lists.linux-foundation.org
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/1471024183-12666-7-git-send-email-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 1b5f531eeb2549483e8a189bcde259a902dd3ca8..fad84f3f41099dce6fb62399b0df9ac6be857318 100644 (file)
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -138,8 +138,9 @@ struct virtnet_info {
        /* Does the affinity hint is set for virtqueues? */
        bool affinity_hint_set;
 
-       /* CPU hot plug notifier */
-       struct notifier_block nb;
+       /* CPU hotplug instances for online & dead */
+       struct hlist_node node;
+       struct hlist_node node_dead;
 
        /* Control VQ buffers: protected by the rtnl lock */
        struct virtio_net_ctrl_hdr ctrl_hdr;
@@ -1237,25 +1238,53 @@ static void virtnet_set_affinity(struct virtnet_info *vi)
        vi->affinity_hint_set = true;
 }
 
-static int virtnet_cpu_callback(struct notifier_block *nfb,
-                               unsigned long action, void *hcpu)
+static int virtnet_cpu_online(unsigned int cpu, struct hlist_node *node)
 {
-       struct virtnet_info *vi = container_of(nfb, struct virtnet_info, nb);
+       struct virtnet_info *vi = hlist_entry_safe(node, struct virtnet_info,
+                                                  node);
+       virtnet_set_affinity(vi);
+       return 0;
+}
 
-       switch(action & ~CPU_TASKS_FROZEN) {
-       case CPU_ONLINE:
-       case CPU_DOWN_FAILED:
-       case CPU_DEAD:
-               virtnet_set_affinity(vi);
-               break;
-       case CPU_DOWN_PREPARE:
-               virtnet_clean_affinity(vi, (long)hcpu);
-               break;
-       default:
-               break;
-       }
+static int virtnet_cpu_dead(unsigned int cpu, struct hlist_node *node)
+{
+       struct virtnet_info *vi = hlist_entry_safe(node, struct virtnet_info,
+                                                  node_dead);
+       virtnet_set_affinity(vi);
+       return 0;
+}
 
-       return NOTIFY_OK;
+static int virtnet_cpu_down_prep(unsigned int cpu, struct hlist_node *node)
+{
+       struct virtnet_info *vi = hlist_entry_safe(node, struct virtnet_info,
+                                                  node);
+
+       virtnet_clean_affinity(vi, cpu);
+       return 0;
+}
+
+static enum cpuhp_state virtionet_online;
+
+static int virtnet_cpu_notif_add(struct virtnet_info *vi)
+{
+       int ret;
+
+       ret = cpuhp_state_add_instance_nocalls(virtionet_online, &vi->node);
+       if (ret)
+               return ret;
+       ret = cpuhp_state_add_instance_nocalls(CPUHP_VIRT_NET_DEAD,
+                                              &vi->node_dead);
+       if (!ret)
+               return ret;
+       cpuhp_state_remove_instance_nocalls(virtionet_online, &vi->node);
+       return ret;
+}
+
+static void virtnet_cpu_notif_remove(struct virtnet_info *vi)
+{
+       cpuhp_state_remove_instance_nocalls(virtionet_online, &vi->node);
+       cpuhp_state_remove_instance_nocalls(CPUHP_VIRT_NET_DEAD,
+                                           &vi->node_dead);
 }
 
 static void virtnet_get_ringparam(struct net_device *dev,
@@ -1879,8 +1908,7 @@ static int virtnet_probe(struct virtio_device *vdev)
 
        virtio_device_ready(vdev);
 
-       vi->nb.notifier_call = &virtnet_cpu_callback;
-       err = register_hotcpu_notifier(&vi->nb);
+       err = virtnet_cpu_notif_add(vi);
        if (err) {
                pr_debug("virtio_net: registering cpu notifier failed\n");
                goto free_unregister_netdev;
@@ -1934,7 +1962,7 @@ static void virtnet_remove(struct virtio_device *vdev)
 {
        struct virtnet_info *vi = vdev->priv;
 
-       unregister_hotcpu_notifier(&vi->nb);
+       virtnet_cpu_notif_remove(vi);
 
        /* Make sure no work handler is accessing the device. */
        flush_work(&vi->config_work);
@@ -1953,7 +1981,7 @@ static int virtnet_freeze(struct virtio_device *vdev)
        struct virtnet_info *vi = vdev->priv;
        int i;
 
-       unregister_hotcpu_notifier(&vi->nb);
+       virtnet_cpu_notif_remove(vi);
 
        /* Make sure no work handler is accessing the device */
        flush_work(&vi->config_work);
@@ -1997,7 +2025,7 @@ static int virtnet_restore(struct virtio_device *vdev)
        virtnet_set_queues(vi, vi->curr_queue_pairs);
        rtnl_unlock();
 
-       err = register_hotcpu_notifier(&vi->nb);
+       err = virtnet_cpu_notif_add(vi);
        if (err)
                return err;
 
@@ -2039,7 +2067,41 @@ static struct virtio_driver virtio_net_driver = {
 #endif
 };
 
-module_virtio_driver(virtio_net_driver);
+static __init int virtio_net_driver_init(void)
+{
+       int ret;
+
+       ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, "AP_VIRT_NET_ONLINE",
+                                     virtnet_cpu_online,
+                                     virtnet_cpu_down_prep);
+       if (ret < 0)
+               goto out;
+       virtionet_online = ret;
+       ret = cpuhp_setup_state_multi(CPUHP_VIRT_NET_DEAD, "VIRT_NET_DEAD",
+                                     NULL, virtnet_cpu_dead);
+       if (ret)
+               goto err_dead;
+
+        ret = register_virtio_driver(&virtio_net_driver);
+       if (ret)
+               goto err_virtio;
+       return 0;
+err_virtio:
+       cpuhp_remove_multi_state(CPUHP_VIRT_NET_DEAD);
+err_dead:
+       cpuhp_remove_multi_state(virtionet_online);
+out:
+       return ret;
+}
+module_init(virtio_net_driver_init);
+
+static __exit void virtio_net_driver_exit(void)
+{
+       cpuhp_remove_multi_state(CPUHP_VIRT_NET_DEAD);
+       cpuhp_remove_multi_state(virtionet_online);
+       unregister_virtio_driver(&virtio_net_driver);
+}
+module_exit(virtio_net_driver_exit);
 
 MODULE_DEVICE_TABLE(virtio, id_table);
 MODULE_DESCRIPTION("Virtio network driver");

diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index dcfe619171b4eafa21c5b26825f59d394adb3cc0..b95f7adfbf8b6adaa10c54bc9cc64d77a8df9d3a 100644 (file)
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -14,6 +14,7 @@ enum cpuhp_state {
        CPUHP_PERF_SUPERH,
        CPUHP_X86_HPET_DEAD,
        CPUHP_X86_APB_DEAD,
+       CPUHP_VIRT_NET_DEAD,
        CPUHP_WORKQUEUE_PREP,
        CPUHP_POWER_NUMA_PREPARE,
        CPUHP_HRTIMERS_PREPARE,