tcm_vhost: Add hotplug/hotunplug support

In commit 365a7150094 ([SCSI] virtio-scsi: hotplug support for
virtio-scsi), hotplug support is added to virtio-scsi.

This patch adds hotplug and hotunplug support to tcm_vhost.

You can create or delete a LUN in targetcli to hotplug or hotunplug a
LUN in guest.

Signed-off-by: Asias He <asias@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

2 files changed, 218 insertions, 2 deletions

diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
index 822cd1fbff5e..5340fd759c6e 100644
--- a/drivers/vhost/tcm_vhost.c
+++ b/drivers/vhost/tcm_vhost.c
@@ -71,6 +71,7 @@ enum {
 
 #define VHOST_SCSI_MAX_TARGET   256
 #define VHOST_SCSI_MAX_VQ       128
+#define VHOST_SCSI_MAX_EVENT    128
 
 struct vhost_scsi {
         /* Protected by vhost_scsi->dev.mutex */
@@ -82,6 +83,12 @@ struct vhost_scsi {
 
         struct vhost_work vs_completion_work; /* cmd completion work item */
         struct llist_head vs_completion_list; /* cmd completion queue */
+
+        struct vhost_work vs_event_work; /* evt injection work item */
+        struct llist_head vs_event_list; /* evt injection queue */
+
+        bool vs_events_missed; /* any missed events, protected by vq->mutex */
+        int vs_events_nr; /* num of pending events, protected by vq->mutex */
 };
 
 /* Local pointer to allocated TCM configfs fabric module */
@@ -349,6 +356,37 @@ static int tcm_vhost_queue_tm_rsp(struct se_cmd *se_cmd)
         return 0;
 }
 
+static void tcm_vhost_free_evt(struct vhost_scsi *vs, struct tcm_vhost_evt *evt)
+{
+        vs->vs_events_nr--;
+        kfree(evt);
+}
+
+static struct tcm_vhost_evt *tcm_vhost_allocate_evt(struct vhost_scsi *vs,
+        u32 event, u32 reason)
+{
+        struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT];
+        struct tcm_vhost_evt *evt;
+
+        if (vs->vs_events_nr > VHOST_SCSI_MAX_EVENT) {
+                vs->vs_events_missed = true;
+                return NULL;
+        }
+
+        evt = kzalloc(sizeof(*evt), GFP_KERNEL);
+        if (!evt) {
+                vq_err(vq, "Failed to allocate tcm_vhost_evt\n");
+                vs->vs_events_missed = true;
+                return NULL;
+        }
+
+        evt->event.event = event;
+        evt->event.reason = reason;
+        vs->vs_events_nr++;
+
+        return evt;
+}
+
 static void vhost_scsi_free_cmd(struct tcm_vhost_cmd *tv_cmd)
 {
         struct se_cmd *se_cmd = &tv_cmd->tvc_se_cmd;
@@ -367,6 +405,75 @@ static void vhost_scsi_free_cmd(struct tcm_vhost_cmd *tv_cmd)
         kfree(tv_cmd);
 }
 
+static void tcm_vhost_do_evt_work(struct vhost_scsi *vs,
+        struct tcm_vhost_evt *evt)
+{
+        struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT];
+        struct virtio_scsi_event *event = &evt->event;
+        struct virtio_scsi_event __user *eventp;
+        unsigned out, in;
+        int head, ret;
+
+        if (!vq->private_data) {
+                vs->vs_events_missed = true;
+                return;
+        }
+
+again:
+        vhost_disable_notify(&vs->dev, vq);
+        head = vhost_get_vq_desc(&vs->dev, vq, vq->iov,
+                        ARRAY_SIZE(vq->iov), &out, &in,
+                        NULL, NULL);
+        if (head < 0) {
+                vs->vs_events_missed = true;
+                return;
+        }
+        if (head == vq->num) {
+                if (vhost_enable_notify(&vs->dev, vq))
+                        goto again;
+                vs->vs_events_missed = true;
+                return;
+        }
+
+        if ((vq->iov[out].iov_len != sizeof(struct virtio_scsi_event))) {
+                vq_err(vq, "Expecting virtio_scsi_event, got %zu bytes\n",
+                                vq->iov[out].iov_len);
+                vs->vs_events_missed = true;
+                return;
+        }
+
+        if (vs->vs_events_missed) {
+                event->event |= VIRTIO_SCSI_T_EVENTS_MISSED;
+                vs->vs_events_missed = false;
+        }
+
+        eventp = vq->iov[out].iov_base;
+        ret = __copy_to_user(eventp, event, sizeof(*event));
+        if (!ret)
+                vhost_add_used_and_signal(&vs->dev, vq, head, 0);
+        else
+                vq_err(vq, "Faulted on tcm_vhost_send_event\n");
+}
+
+static void tcm_vhost_evt_work(struct vhost_work *work)
+{
+        struct vhost_scsi *vs = container_of(work, struct vhost_scsi,
+                                        vs_event_work);
+        struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT];
+        struct tcm_vhost_evt *evt;
+        struct llist_node *llnode;
+
+        mutex_lock(&vq->mutex);
+        llnode = llist_del_all(&vs->vs_event_list);
+        while (llnode) {
+                evt = llist_entry(llnode, struct tcm_vhost_evt, list);
+                llnode = llist_next(llnode);
+                tcm_vhost_do_evt_work(vs, evt);
+                tcm_vhost_free_evt(vs, evt);
+        }
+        mutex_unlock(&vq->mutex);
+}
+
 /* Fill in status and signal that we are done processing this command
  *
  * This is scheduled in the vhost work queue so we are called with the owner
@@ -777,9 +884,46 @@ static void vhost_scsi_ctl_handle_kick(struct vhost_work *work)
         pr_debug("%s: The handling func for control queue.\n", __func__);
 }
 
+static void tcm_vhost_send_evt(struct vhost_scsi *vs, struct tcm_vhost_tpg *tpg,
+        struct se_lun *lun, u32 event, u32 reason)
+{
+        struct tcm_vhost_evt *evt;
+
+        evt = tcm_vhost_allocate_evt(vs, event, reason);
+        if (!evt)
+                return;
+
+        if (tpg && lun) {
+                /* TODO: share lun setup code with virtio-scsi.ko */
+                /*
+                 * Note: evt->event is zeroed when we allocate it and
+                 * lun[4-7] need to be zero according to virtio-scsi spec.
+                 */
+                evt->event.lun[0] = 0x01;
+                evt->event.lun[1] = tpg->tport_tpgt & 0xFF;
+                if (lun->unpacked_lun >= 256)
+                        evt->event.lun[2] = lun->unpacked_lun >> 8 | 0x40 ;
+                evt->event.lun[3] = lun->unpacked_lun & 0xFF;
+        }
+
+        llist_add(&evt->list, &vs->vs_event_list);
+        vhost_work_queue(&vs->dev, &vs->vs_event_work);
+}
+
 static void vhost_scsi_evt_handle_kick(struct vhost_work *work)
 {
-        pr_debug("%s: The handling func for event queue.\n", __func__);
+        struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
+                                                poll.work);
+        struct vhost_scsi *vs = container_of(vq->dev, struct vhost_scsi, dev);
+
+        mutex_lock(&vq->mutex);
+        if (!vq->private_data)
+                goto out;
+
+        if (vs->vs_events_missed)
+                tcm_vhost_send_evt(vs, NULL, NULL, VIRTIO_SCSI_T_NO_EVENT, 0);
+out:
+        mutex_unlock(&vq->mutex);
 }
 
 static void vhost_scsi_handle_kick(struct vhost_work *work)
@@ -803,6 +947,7 @@ static void vhost_scsi_flush(struct vhost_scsi *vs)
         for (i = 0; i < VHOST_SCSI_MAX_VQ; i++)
                 vhost_scsi_flush_vq(vs, i);
         vhost_work_flush(&vs->dev, &vs->vs_completion_work);
+        vhost_work_flush(&vs->dev, &vs->vs_event_work);
 }
 
 /*
@@ -864,6 +1009,7 @@ static int vhost_scsi_set_endpoint(
                                 goto out;
                         }
                         tv_tpg->tv_tpg_vhost_count++;
+                        tv_tpg->vhost_scsi = vs;
                         vs_tpg[tv_tpg->tport_tpgt] = tv_tpg;
                         smp_mb__after_atomic_inc();
                         match = true;
@@ -949,6 +1095,7 @@ static int vhost_scsi_clear_endpoint(
                         goto err_tpg;
                 }
                 tv_tpg->tv_tpg_vhost_count--;
+                tv_tpg->vhost_scsi = NULL;
                 vs->vs_tpg[target] = NULL;
                 match = true;
                 mutex_unlock(&tv_tpg->tv_tpg_mutex);
@@ -969,6 +1116,7 @@ static int vhost_scsi_clear_endpoint(
         vhost_scsi_flush(vs);
         kfree(vs->vs_tpg);
         vs->vs_tpg = NULL;
+        WARN_ON(vs->vs_events_nr);
         mutex_unlock(&vs->dev.mutex);
         mutex_unlock(&tcm_vhost_mutex);
         return 0;
@@ -1009,6 +1157,10 @@ static int vhost_scsi_open(struct inode *inode, struct file *f)
                 return -ENOMEM;
 
         vhost_work_init(&s->vs_completion_work, vhost_scsi_complete_cmd_work);
+        vhost_work_init(&s->vs_event_work, tcm_vhost_evt_work);
+
+        s->vs_events_nr = 0;
+        s->vs_events_missed = false;
 
         s->vqs[VHOST_SCSI_VQ_CTL].handle_kick = vhost_scsi_ctl_handle_kick;
         s->vqs[VHOST_SCSI_VQ_EVT].handle_kick = vhost_scsi_evt_handle_kick;
@@ -1035,6 +1187,8 @@ static int vhost_scsi_release(struct inode *inode, struct file *f)
         vhost_scsi_clear_endpoint(s, &t);
         vhost_dev_stop(&s->dev);
         vhost_dev_cleanup(&s->dev, false);
+        /* Jobs can re-queue themselves in evt kick handler. Do extra flush. */
+        vhost_scsi_flush(s);
         kfree(s);
         return 0;
 }
@@ -1139,28 +1293,80 @@ static char *tcm_vhost_dump_proto_id(struct tcm_vhost_tport *tport)
         return "Unknown";
 }
 
+static void tcm_vhost_do_plug(struct tcm_vhost_tpg *tpg,
+        struct se_lun *lun, bool plug)
+{
+
+        struct vhost_scsi *vs = tpg->vhost_scsi;
+        struct vhost_virtqueue *vq;
+        u32 reason;
+
+        if (!vs)
+                return;
+
+        mutex_lock(&vs->dev.mutex);
+        if (!vhost_has_feature(&vs->dev, VIRTIO_SCSI_F_HOTPLUG)) {
+                mutex_unlock(&vs->dev.mutex);
+                return;
+        }
+
+        if (plug)
+                reason = VIRTIO_SCSI_EVT_RESET_RESCAN;
+        else
+                reason = VIRTIO_SCSI_EVT_RESET_REMOVED;
+
+        vq = &vs->vqs[VHOST_SCSI_VQ_EVT];
+        mutex_lock(&vq->mutex);
+        tcm_vhost_send_evt(vs, tpg, lun,
+                        VIRTIO_SCSI_T_TRANSPORT_RESET, reason);
+        mutex_unlock(&vq->mutex);
+        mutex_unlock(&vs->dev.mutex);
+}
+
+static void tcm_vhost_hotplug(struct tcm_vhost_tpg *tpg, struct se_lun *lun)
+{
+        tcm_vhost_do_plug(tpg, lun, true);
+}
+
+static void tcm_vhost_hotunplug(struct tcm_vhost_tpg *tpg, struct se_lun *lun)
+{
+        tcm_vhost_do_plug(tpg, lun, false);
+}
+
 static int tcm_vhost_port_link(struct se_portal_group *se_tpg,
         struct se_lun *lun)
 {
         struct tcm_vhost_tpg *tv_tpg = container_of(se_tpg,
                                 struct tcm_vhost_tpg, se_tpg);
 
+        mutex_lock(&tcm_vhost_mutex);
+
         mutex_lock(&tv_tpg->tv_tpg_mutex);
         tv_tpg->tv_tpg_port_count++;
         mutex_unlock(&tv_tpg->tv_tpg_mutex);
 
+        tcm_vhost_hotplug(tv_tpg, lun);
+
+        mutex_unlock(&tcm_vhost_mutex);
+
         return 0;
 }
 
 static void tcm_vhost_port_unlink(struct se_portal_group *se_tpg,
-        struct se_lun *se_lun)
+        struct se_lun *lun)
 {
         struct tcm_vhost_tpg *tv_tpg = container_of(se_tpg,
                                 struct tcm_vhost_tpg, se_tpg);
 
+        mutex_lock(&tcm_vhost_mutex);
+
         mutex_lock(&tv_tpg->tv_tpg_mutex);
         tv_tpg->tv_tpg_port_count--;
         mutex_unlock(&tv_tpg->tv_tpg_mutex);
+
+        tcm_vhost_hotunplug(tv_tpg, lun);
+
+        mutex_unlock(&tcm_vhost_mutex);
 }
 
 static struct se_node_acl *tcm_vhost_make_nodeacl(
diff --git a/drivers/vhost/tcm_vhost.h b/drivers/vhost/tcm_vhost.h
index 1d2ae7a60e11..a545a5b766a3 100644
--- a/drivers/vhost/tcm_vhost.h
+++ b/drivers/vhost/tcm_vhost.h
@@ -53,6 +53,7 @@ struct tcm_vhost_nacl {
         struct se_node_acl se_node_acl;
 };
 
+struct vhost_scsi;
 struct tcm_vhost_tpg {
         /* Vhost port target portal group tag for TCM */
         u16 tport_tpgt;
@@ -70,6 +71,8 @@ struct tcm_vhost_tpg {
         struct tcm_vhost_tport *tport;
         /* Returned by tcm_vhost_make_tpg() */
         struct se_portal_group se_tpg;
+        /* Pointer back to vhost_scsi, protected by tv_tpg_mutex */
+        struct vhost_scsi *vhost_scsi;
 };
 
 struct tcm_vhost_tport {
@@ -83,6 +86,13 @@ struct tcm_vhost_tport {
         struct se_wwn tport_wwn;
 };
 
+struct tcm_vhost_evt {
+        /* event to be sent to guest */
+        struct virtio_scsi_event event;
+        /* event list, serviced from vhost worker thread */
+        struct llist_node list;
+};
+
 /*
  * As per request from MST, keep TCM_VHOST related ioctl defines out of
  * linux/vhost.h (user-space) for now..