vhost/scsi: Respond to control queue operations
authorBijan Mottahedeh <bijan.mottahedeh@oracle.com>
Tue, 18 Sep 2018 00:09:47 +0000 (17:09 -0700)
committerMichael S. Tsirkin <mst@redhat.com>
Thu, 25 Oct 2018 01:16:13 +0000 (21:16 -0400)
The vhost-scsi driver currently does not handle any control queue
operations. In particular, vhost_scsi_ctl_handle_kick, merely prints out
a debug message but does nothing else. This can cause guest VMs to hang.

As part of SCSI recovery from an error, e.g., an I/O timeout, the SCSI
midlayer attempts to abort the failed operation. The SCSI virtio driver
translates the abort to a SCSI TMF request that gets put on the control
queue (virtscsi_abort -> virtscsi_tmf). The SCSI virtio driver then
waits indefinitely for this request to be completed, but it never will
because vhost-scsi never responds to that request.

To avoid a hang, always respond to control queue operations; explicitly
reject TMF requests, and return a no-op response to event requests.

Signed-off-by: Bijan Mottahedeh <bijan.mottahedeh@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
drivers/vhost/scsi.c

index e7e3ae13516d7d69f37724cf5c5ce9c2b7790f51..1c33d6e391525d4fa36517e5de9d5fa8b8ef8277 100644 (file)
@@ -1050,9 +1050,199 @@ out:
        mutex_unlock(&vq->mutex);
 }
 
+static void
+vhost_scsi_send_tmf_resp(struct vhost_scsi *vs,
+                          struct vhost_virtqueue *vq,
+                          int head, unsigned int out)
+{
+       struct virtio_scsi_ctrl_tmf_resp __user *resp;
+       struct virtio_scsi_ctrl_tmf_resp rsp;
+       int ret;
+
+       pr_debug("%s\n", __func__);
+       memset(&rsp, 0, sizeof(rsp));
+       rsp.response = VIRTIO_SCSI_S_FUNCTION_REJECTED;
+       resp = vq->iov[out].iov_base;
+       ret = __copy_to_user(resp, &rsp, sizeof(rsp));
+       if (!ret)
+               vhost_add_used_and_signal(&vs->dev, vq, head, 0);
+       else
+               pr_err("Faulted on virtio_scsi_ctrl_tmf_resp\n");
+}
+
+static void
+vhost_scsi_send_an_resp(struct vhost_scsi *vs,
+                          struct vhost_virtqueue *vq,
+                          int head, unsigned int out)
+{
+       struct virtio_scsi_ctrl_an_resp __user *resp;
+       struct virtio_scsi_ctrl_an_resp rsp;
+       int ret;
+
+       pr_debug("%s\n", __func__);
+       memset(&rsp, 0, sizeof(rsp));   /* event_actual = 0 */
+       rsp.response = VIRTIO_SCSI_S_OK;
+       resp = vq->iov[out].iov_base;
+       ret = __copy_to_user(resp, &rsp, sizeof(rsp));
+       if (!ret)
+               vhost_add_used_and_signal(&vs->dev, vq, head, 0);
+       else
+               pr_err("Faulted on virtio_scsi_ctrl_an_resp\n");
+}
+
+static void
+vhost_scsi_ctl_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
+{
+       union {
+               __virtio32 type;
+               struct virtio_scsi_ctrl_an_req an;
+               struct virtio_scsi_ctrl_tmf_req tmf;
+       } v_req;
+       struct iov_iter out_iter;
+       unsigned int out = 0, in = 0;
+       int head;
+       size_t req_size, rsp_size, typ_size;
+       size_t out_size, in_size;
+       u8 *lunp;
+       void *req;
+
+       mutex_lock(&vq->mutex);
+       /*
+        * We can handle the vq only after the endpoint is setup by calling the
+        * VHOST_SCSI_SET_ENDPOINT ioctl.
+        */
+       if (!vq->private_data)
+               goto out;
+
+       vhost_disable_notify(&vs->dev, vq);
+
+       for (;;) {
+               head = vhost_get_vq_desc(vq, vq->iov,
+                                        ARRAY_SIZE(vq->iov), &out, &in,
+                                        NULL, NULL);
+               pr_debug("vhost_get_vq_desc: head: %d, out: %u in: %u\n",
+                        head, out, in);
+               /* On error, stop handling until the next kick. */
+               if (unlikely(head < 0))
+                       break;
+               /* Nothing new?  Wait for eventfd to tell us they refilled. */
+               if (head == vq->num) {
+                       if (unlikely(vhost_enable_notify(&vs->dev, vq))) {
+                               vhost_disable_notify(&vs->dev, vq);
+                               continue;
+                       }
+                       break;
+               }
+
+               /*
+                * Get the size of request and response buffers.
+                */
+               out_size = iov_length(vq->iov, out);
+               in_size = iov_length(&vq->iov[out], in);
+
+               /*
+                * Copy over the virtio-scsi request header, which for a
+                * ANY_LAYOUT enabled guest may span multiple iovecs, or a
+                * single iovec may contain both the header + outgoing
+                * WRITE payloads.
+                *
+                * copy_from_iter() will advance out_iter, so that it will
+                * point at the start of the outgoing WRITE payload, if
+                * DMA_TO_DEVICE is set.
+                */
+               iov_iter_init(&out_iter, WRITE, vq->iov, out, out_size);
+
+               req = &v_req.type;
+               typ_size = sizeof(v_req.type);
+
+               if (unlikely(!copy_from_iter_full(req, typ_size, &out_iter))) {
+                       vq_err(vq, "Faulted on copy_from_iter tmf type\n");
+                       /*
+                        * The size of the response buffer varies based on
+                        * the request type and must be validated against it.
+                        * Since the request type is not known, don't send
+                        * a response.
+                        */
+                       continue;
+               }
+
+               switch (v_req.type) {
+               case VIRTIO_SCSI_T_TMF:
+                       req = &v_req.tmf;
+                       lunp = &v_req.tmf.lun[0];
+                       req_size = sizeof(struct virtio_scsi_ctrl_tmf_req);
+                       rsp_size = sizeof(struct virtio_scsi_ctrl_tmf_resp);
+                       break;
+               case VIRTIO_SCSI_T_AN_QUERY:
+               case VIRTIO_SCSI_T_AN_SUBSCRIBE:
+                       req = &v_req.an;
+                       lunp = &v_req.an.lun[0];
+                       req_size = sizeof(struct virtio_scsi_ctrl_an_req);
+                       rsp_size = sizeof(struct virtio_scsi_ctrl_an_resp);
+                       break;
+               default:
+                       vq_err(vq, "Unknown control request %d", v_req.type);
+                       continue;
+               }
+
+               /*
+                * Check for a sane response buffer so we can report early
+                * errors back to the guest.
+                */
+               if (unlikely(in_size < rsp_size)) {
+                       vq_err(vq,
+                              "Resp buf too small, need min %zu bytes got %zu",
+                              rsp_size, in_size);
+                       /*
+                        * Notifications are disabled at this point;
+                        * continue so they can be eventually enabled
+                        * when processing terminates.
+                        */
+                       continue;
+               }
+
+               if (unlikely(out_size < req_size)) {
+                       vq_err(vq,
+                              "Req buf too small, need min %zu bytes got %zu",
+                              req_size, out_size);
+                       vhost_scsi_send_bad_target(vs, vq, head, out);
+                       continue;
+               }
+
+               req += typ_size;
+               req_size -= typ_size;
+
+               if (unlikely(!copy_from_iter_full(req, req_size, &out_iter))) {
+                       vq_err(vq, "Faulted on copy_from_iter\n");
+                       vhost_scsi_send_bad_target(vs, vq, head, out);
+                       continue;
+               }
+
+               /* virtio-scsi spec requires byte 0 of the lun to be 1 */
+               if (unlikely(*lunp != 1)) {
+                       vq_err(vq, "Illegal virtio-scsi lun: %u\n", *lunp);
+                       vhost_scsi_send_bad_target(vs, vq, head, out);
+                       continue;
+               }
+
+               if (v_req.type == VIRTIO_SCSI_T_TMF) {
+                       pr_debug("%s tmf %d\n", __func__, v_req.tmf.subtype);
+                       vhost_scsi_send_tmf_resp(vs, vq, head, out);
+               } else
+                       vhost_scsi_send_an_resp(vs, vq, head, out);
+       }
+out:
+       mutex_unlock(&vq->mutex);
+}
+
 static void vhost_scsi_ctl_handle_kick(struct vhost_work *work)
 {
+       struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
+                                               poll.work);
+       struct vhost_scsi *vs = container_of(vq->dev, struct vhost_scsi, dev);
+
        pr_debug("%s: The handling func for control queue.\n", __func__);
+       vhost_scsi_ctl_handle_vq(vs, vq);
 }
 
 static void