On Thu, Jul 26, 2012 at 4:43 PM, Nicholas A. Bellinger
<address@hidden> wrote:
[...]
+static void vhost_scsi_handle_vq(struct vhost_scsi *vs)
+{
+ struct vhost_virtqueue *vq = &vs->vqs[2];
+ struct virtio_scsi_cmd_req v_req;
+ struct tcm_vhost_tpg *tv_tpg;
+ struct tcm_vhost_cmd *tv_cmd;
+ u32 exp_data_len, data_first, data_num, data_direction;
+ unsigned out, in, i;
+ int head, ret;
+
+ /* Must use ioctl VHOST_SCSI_SET_ENDPOINT */
+ tv_tpg = vs->vs_tpg;
+ if (unlikely(!tv_tpg)) {
+ pr_err("%s endpoint not set\n", __func__);
+ return;
+ }
+
+ mutex_lock(&vq->mutex);
+ vhost_disable_notify(&vs->dev, vq);
+
+ for (;;) {
+ head = vhost_get_vq_desc(&vs->dev, 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;
+ }
+
+/* FIXME: BIDI operation */
+ if (out == 1 && in == 1) {
It seems to me like this is not the way that virtio devices are supposed to behave - if a guest splits a virtio_scsi_cmd_req or _resp across a page boundary, then this code won't work.
Quoting the 'Message Framing' part of the virtio spec:
"In particular, no implementation should use the descriptor boundaries to determine the size of any header in a request. "
+ data_direction = DMA_NONE;
+ data_first = 0;
+ data_num = 0;
+ } else if (out == 1 && in > 1) {
+ data_direction = DMA_FROM_DEVICE;
+ data_first = out + 1;
+ data_num = in - 1;
+ } else if (out > 1 && in == 1) {
+ data_direction = DMA_TO_DEVICE;
+ data_first = 1;
+ data_num = out - 1;
+ } else {
+ vq_err(vq, "Invalid buffer layout out: %u in: %u\n",
+ out, in);
+ break;
+ }
+
+ /*
+ * Check for a sane resp buffer so we can report errors to
+ * the guest.
+ */
+ if (unlikely(vq->iov[out].iov_len !=
+ sizeof(struct virtio_scsi_cmd_resp))) {
+ vq_err(vq, "Expecting virtio_scsi_cmd_resp, got %zu"
+ " bytes\n", vq->iov[out].iov_len);
+ break;
+ }
+
+ if (unlikely(vq->iov[0].iov_len != sizeof(v_req))) {
+ vq_err(vq, "Expecting virtio_scsi_cmd_req, got %zu"
+ " bytes\n", vq->iov[0].iov_len);
+ break;
+ }
+ pr_debug("Calling __copy_from_user: vq->iov[0].iov_base: %p,"
+ " len: %zu\n", vq->iov[0].iov_base, sizeof(v_req));
+ ret = __copy_from_user(&v_req, vq->iov[0].iov_base,
+ sizeof(v_req));
+ if (unlikely(ret)) {
+ vq_err(vq, "Faulted on virtio_scsi_cmd_req\n");
+ break;
+ }
+
+ exp_data_len = 0;
+ for (i = 0; i < data_num; i++)
+ exp_data_len += vq->iov[data_first + i].iov_len;
+
+ tv_cmd = vhost_scsi_allocate_cmd(tv_tpg, &v_req,
+ exp_data_len, data_direction);
+ if (IS_ERR(tv_cmd)) {
+ vq_err(vq, "vhost_scsi_allocate_cmd failed %ld\n",
+ PTR_ERR(tv_cmd));
+ break;
+ }
+ pr_debug("Allocated tv_cmd: %p exp_data_len: %d, data_direction"
+ ": %d\n", tv_cmd, exp_data_len, data_direction);
+
+ tv_cmd->tvc_vhost = vs;
+
+ if (unlikely(vq->iov[out].iov_len !=
+ sizeof(struct virtio_scsi_cmd_resp))) {
+ vq_err(vq, "Expecting virtio_scsi_cmd_resp, got %zu"
+ " bytes, out: %d, in: %d\n",
+ vq->iov[out].iov_len, out, in);
+ break;
+ }
+
+ tv_cmd->tvc_resp = vq->iov[out].iov_base;
+
+ /*
+ * Copy in the recieved CDB descriptor into tv_cmd->tvc_cdb
+ * that will be used by tcm_vhost_new_cmd_map() and down into
+ * target_setup_cmd_from_cdb()
+ */
+ memcpy(tv_cmd->tvc_cdb, v_req.cdb, TCM_VHOST_MAX_CDB_SIZE);
+ /*
+ * Check that the recieved CDB size does not exceeded our
+ * hardcoded max for tcm_vhost
+ */
+ /* TODO what if cdb was too small for varlen cdb header? */
+ if (unlikely(scsi_command_size(tv_cmd->tvc_cdb) >
+ TCM_VHOST_MAX_CDB_SIZE)) {
+ vq_err(vq, "Received SCSI CDB with command_size: %d that"
+ " exceeds SCSI_MAX_VARLEN_CDB_SIZE: %d\n",
+ scsi_command_size(tv_cmd->tvc_cdb),
+ TCM_VHOST_MAX_CDB_SIZE);
+ break; /* TODO */
+ }
+ tv_cmd->tvc_lun = ((v_req.lun[2] << 8) | v_req.lun[3]) & 0x3FFF;
+
+ pr_debug("vhost_scsi got command opcode: %#02x, lun: %d\n",
+ tv_cmd->tvc_cdb[0], tv_cmd->tvc_lun);
+
+ if (data_direction != DMA_NONE) {
+ ret = vhost_scsi_map_iov_to_sgl(tv_cmd,
+ &vq->iov[data_first], data_num,
+ data_direction == DMA_TO_DEVICE);
+ if (unlikely(ret)) {
+ vq_err(vq, "Failed to map iov to sgl\n");
+ break; /* TODO */
+ }
+ }
+
+ /*
+ * Save the descriptor from vhost_get_vq_desc() to be used to
+ * complete the virtio-scsi request in TCM callback context via
+ * tcm_vhost_queue_data_in() and tcm_vhost_queue_status()
+ */
+ tv_cmd->tvc_vq_desc = head;
+ /*
+ * Dispatch tv_cmd descriptor for cmwq execution in process
+ * context provided by tcm_vhost_workqueue. This also ensures
+ * tv_cmd is executed on the same kworker CPU as this vhost
+ * thread to gain positive L2 cache locality effects..
+ */
+ INIT_WORK(&tv_cmd->work, tcm_vhost_submission_work);
+ queue_work(tcm_vhost_workqueue, &tv_cmd->work);
+ }
+
+ mutex_unlock(&vq->mutex);
+}
[...]
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