[SCSI] virtio-scsi: hotplug support for virtio-scsi

This patch implements the hotplug support for virtio-scsi.
When there is a device attached/detached, the virtio-scsi driver will be
signaled via event virtual queue and it will add/remove the scsi device
in question automatically.

Signed-off-by: Sen Wang <senwang@linux.vnet.ibm.com>
Signed-off-by: Cong Meng <mc@linux.vnet.ibm.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

2 files changed, 132 insertions, 1 deletions

diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
index 9fc5e67a0ca5..ae3bef7c523f 100644
--- a/drivers/scsi/virtio_scsi.c
+++ b/drivers/scsi/virtio_scsi.c
@@ -25,6 +25,7 @@
 #include <scsi/scsi_cmnd.h>
 
 #define VIRTIO_SCSI_MEMPOOL_SZ 64
+#define VIRTIO_SCSI_EVENT_LEN 8
 
 /* Command queue element */
 struct virtio_scsi_cmd {
@@ -43,6 +44,12 @@ struct virtio_scsi_cmd {
         } resp;
 } ____cacheline_aligned_in_smp;
 
+struct virtio_scsi_event_node {
+        struct virtio_scsi *vscsi;
+        struct virtio_scsi_event event;
+        struct work_struct work;
+};
+
 struct virtio_scsi_vq {
         /* Protects vq */
         spinlock_t vq_lock;
@@ -67,6 +74,9 @@ struct virtio_scsi {
         struct virtio_scsi_vq event_vq;
         struct virtio_scsi_vq req_vq;
 
+        /* Get some buffers ready for event vq */
+        struct virtio_scsi_event_node event_list[VIRTIO_SCSI_EVENT_LEN];
+
         struct virtio_scsi_target_state *tgt[];
 };
 
@@ -202,6 +212,105 @@ static void virtscsi_ctrl_done(struct virtqueue *vq)
         spin_unlock_irqrestore(&vscsi->ctrl_vq.vq_lock, flags);
 };
 
+static int virtscsi_kick_event(struct virtio_scsi *vscsi,
+                               struct virtio_scsi_event_node *event_node)
+{
+        int ret;
+        struct scatterlist sg;
+        unsigned long flags;
+
+        sg_set_buf(&sg, &event_node->event, sizeof(struct virtio_scsi_event));
+
+        spin_lock_irqsave(&vscsi->event_vq.vq_lock, flags);
+
+        ret = virtqueue_add_buf(vscsi->event_vq.vq, &sg, 0, 1, event_node, GFP_ATOMIC);
+        if (ret >= 0)
+                virtqueue_kick(vscsi->event_vq.vq);
+
+        spin_unlock_irqrestore(&vscsi->event_vq.vq_lock, flags);
+
+        return ret;
+}
+
+static int virtscsi_kick_event_all(struct virtio_scsi *vscsi)
+{
+        int i;
+
+        for (i = 0; i < VIRTIO_SCSI_EVENT_LEN; i++) {
+                vscsi->event_list[i].vscsi = vscsi;
+                virtscsi_kick_event(vscsi, &vscsi->event_list[i]);
+        }
+
+        return 0;
+}
+
+static void virtscsi_cancel_event_work(struct virtio_scsi *vscsi)
+{
+        int i;
+
+        for (i = 0; i < VIRTIO_SCSI_EVENT_LEN; i++)
+                cancel_work_sync(&vscsi->event_list[i].work);
+}
+
+static void virtscsi_handle_transport_reset(struct virtio_scsi *vscsi,
+                                                struct virtio_scsi_event *event)
+{
+        struct scsi_device *sdev;
+        struct Scsi_Host *shost = virtio_scsi_host(vscsi->vdev);
+        unsigned int target = event->lun[1];
+        unsigned int lun = (event->lun[2] << 8) | event->lun[3];
+
+        switch (event->reason) {
+        case VIRTIO_SCSI_EVT_RESET_RESCAN:
+                scsi_add_device(shost, 0, target, lun);
+                break;
+        case VIRTIO_SCSI_EVT_RESET_REMOVED:
+                sdev = scsi_device_lookup(shost, 0, target, lun);
+                if (sdev) {
+                        scsi_remove_device(sdev);
+                        scsi_device_put(sdev);
+                } else {
+                        pr_err("SCSI device %d 0 %d %d not found\n",
+                                shost->host_no, target, lun);
+                }
+                break;
+        default:
+                pr_info("Unsupport virtio scsi event reason %x\n", event->reason);
+        }
+}
+
+static void virtscsi_handle_event(struct work_struct *work)
+{
+        struct virtio_scsi_event_node *event_node =
+                container_of(work, struct virtio_scsi_event_node, work);
+        struct virtio_scsi *vscsi = event_node->vscsi;
+        struct virtio_scsi_event *event = &event_node->event;
+
+        if (event->event & VIRTIO_SCSI_T_EVENTS_MISSED) {
+                event->event &= ~VIRTIO_SCSI_T_EVENTS_MISSED;
+                scsi_scan_host(virtio_scsi_host(vscsi->vdev));
+        }
+
+        switch (event->event) {
+        case VIRTIO_SCSI_T_NO_EVENT:
+                break;
+        case VIRTIO_SCSI_T_TRANSPORT_RESET:
+                virtscsi_handle_transport_reset(vscsi, event);
+                break;
+        default:
+                pr_err("Unsupport virtio scsi event %x\n", event->event);
+        }
+        virtscsi_kick_event(vscsi, event_node);
+}
+
+static void virtscsi_complete_event(void *buf)
+{
+        struct virtio_scsi_event_node *event_node = buf;
+
+        INIT_WORK(&event_node->work, virtscsi_handle_event);
+        schedule_work(&event_node->work);
+}
+
 static void virtscsi_event_done(struct virtqueue *vq)
 {
         struct Scsi_Host *sh = virtio_scsi_host(vq->vdev);
@@ -209,7 +318,7 @@ static void virtscsi_event_done(struct virtqueue *vq)
         unsigned long flags;
 
         spin_lock_irqsave(&vscsi->event_vq.vq_lock, flags);
-        virtscsi_vq_done(vq, virtscsi_complete_free);
+        virtscsi_vq_done(vq, virtscsi_complete_event);
         spin_unlock_irqrestore(&vscsi->event_vq.vq_lock, flags);
 };
 
@@ -510,6 +619,9 @@ static int virtscsi_init(struct virtio_device *vdev,
         virtscsi_config_set(vdev, cdb_size, VIRTIO_SCSI_CDB_SIZE);
         virtscsi_config_set(vdev, sense_size, VIRTIO_SCSI_SENSE_SIZE);
 
+        if (virtio_has_feature(vdev, VIRTIO_SCSI_F_HOTPLUG))
+                virtscsi_kick_event_all(vscsi);
+
         /* We need to know how many segments before we allocate.  */
         sg_elems = virtscsi_config_get(vdev, seg_max) ?: 1;
 
@@ -580,6 +692,10 @@ virtscsi_init_failed:
 static void __devexit virtscsi_remove(struct virtio_device *vdev)
 {
         struct Scsi_Host *shost = virtio_scsi_host(vdev);
+        struct virtio_scsi *vscsi = shost_priv(shost);
+
+        if (virtio_has_feature(vdev, VIRTIO_SCSI_F_HOTPLUG))
+                virtscsi_cancel_event_work(vscsi);
 
         scsi_remove_host(shost);
 
@@ -608,7 +724,13 @@ static struct virtio_device_id id_table[] = {
         { 0 },
 };
 
+static unsigned int features[] = {
+        VIRTIO_SCSI_F_HOTPLUG
+};
+
 static struct virtio_driver virtio_scsi_driver = {
+        .feature_table = features,
+        .feature_table_size = ARRAY_SIZE(features),
         .driver.name = KBUILD_MODNAME,
         .driver.owner = THIS_MODULE,
         .id_table = id_table,
diff --git a/include/linux/virtio_scsi.h b/include/linux/virtio_scsi.h
index 8ddeafdc0546..dc8d305b0e05 100644
--- a/include/linux/virtio_scsi.h
+++ b/include/linux/virtio_scsi.h
@@ -69,6 +69,10 @@ struct virtio_scsi_config {
         u32 max_lun;
 } __packed;
 
+/* Feature Bits */
+#define VIRTIO_SCSI_F_INOUT                    0
+#define VIRTIO_SCSI_F_HOTPLUG                  1
+
 /* Response codes */
 #define VIRTIO_SCSI_S_OK                       0
 #define VIRTIO_SCSI_S_OVERRUN                  1
@@ -105,6 +109,11 @@ struct virtio_scsi_config {
 #define VIRTIO_SCSI_T_TRANSPORT_RESET          1
 #define VIRTIO_SCSI_T_ASYNC_NOTIFY             2
 
+/* Reasons of transport reset event */
+#define VIRTIO_SCSI_EVT_RESET_HARD             0
+#define VIRTIO_SCSI_EVT_RESET_RESCAN           1
+#define VIRTIO_SCSI_EVT_RESET_REMOVED          2
+
 #define VIRTIO_SCSI_S_SIMPLE                   0
 #define VIRTIO_SCSI_S_ORDERED                  1
 #define VIRTIO_SCSI_S_HEAD                     2