[PATCH 4/9] vhost-scsi: log I/O queue write descriptors

[Dongli Zhang]

Log write descriptors for the I/O queue, leveraging vhost_scsi_get_desc()
and vhost_get_vq_desc() to retrieve the array of write descriptors to
obtain the log buffer.

In addition, introduce a vhost-scsi specific function to log vring
descriptors. In this function, the 'partial' argument is set to false, and
the 'len' argument is set to 0, because vhost-scsi always logs all pages
shared by a vring descriptor. Add WARN_ON_ONCE() since vhost-scsi doesn't
support VIRTIO_F_ACCESS_PLATFORM.

Store the log buffer during the submission path and log it in the
completion path. Logging is also required in the error handling path of the
submission process.

While the submission path is already protected by vq->mutex, the completion
path also requires this lock for synchronization.

Suggested-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
Signed-off-by: Dongli Zhang <dongli.zhang@xxxxxxxxxx>
---
 drivers/vhost/scsi.c | 41 +++++++++++++++++++++++++++++++++++++++--
 1 file changed, 39 insertions(+), 2 deletions(-)

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 5e6221cbbe9e..d678eaf4ca68 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -329,6 +329,24 @@ static int vhost_scsi_check_prot_fabric_only(struct se_portal_group *se_tpg)
 	return tpg->tv_fabric_prot_type;
 }
 
+static void vhost_scsi_log_write(struct vhost_virtqueue *vq,
+				 struct vhost_log *log,
+				 unsigned int log_num)
+{
+	if (likely(!log || !log_num))
+		return;
+
+	if (likely(!vhost_has_feature(vq, VHOST_F_LOG_ALL)))
+		return;
+
+	/*
+	 * vhost-scsi doesn't support VIRTIO_F_ACCESS_PLATFORM.
+	 * No requirement for vq->iotlb case.
+	 */
+	WARN_ON_ONCE(unlikely(vq->iotlb));
+	vhost_log_write(vq, log, log_num, 0, false, NULL, 0);
+}
+
 static void vhost_scsi_release_cmd_res(struct se_cmd *se_cmd)
 {
 	struct vhost_scsi_cmd *tv_cmd = container_of(se_cmd,
@@ -606,6 +624,13 @@ static void vhost_scsi_complete_cmd_work(struct vhost_work *work)
 		} else
 			pr_err("Faulted on virtio_scsi_cmd_resp\n");
 
+		if (unlikely(cmd->tvc_log_num)) {
+			mutex_lock(&cmd->tvc_vq->mutex);
+			vhost_scsi_log_write(cmd->tvc_vq, cmd->tvc_log,
+					     cmd->tvc_log_num);
+			mutex_unlock(&cmd->tvc_vq->mutex);
+		}
+
 		vhost_scsi_release_cmd_res(se_cmd);
 	}
 
@@ -1082,6 +1107,8 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
 	u8 task_attr;
 	bool t10_pi = vhost_has_feature(vq, VIRTIO_SCSI_F_T10_PI);
 	void *cdb;
+	struct vhost_log *vq_log;
+	unsigned int log_num;
 
 	mutex_lock(&vq->mutex);
 	/*
@@ -1097,8 +1124,11 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
 
 	vhost_disable_notify(&vs->dev, vq);
 
+	vq_log = unlikely(vhost_has_feature(vq, VHOST_F_LOG_ALL)) ?
+		vq->log : NULL;
+
 	do {
-		ret = vhost_scsi_get_desc(vs, vq, &vc, NULL, NULL);
+		ret = vhost_scsi_get_desc(vs, vq, &vc, vq_log, &log_num);
 		if (ret)
 			goto err;
 
@@ -1238,6 +1268,11 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
 			cmd->tvc_resp_iov[i] = vq->iov[vc.out + i];
 		cmd->tvc_in_iovs = vc.in;
 
+		if (unlikely(vq_log && log_num)) {
+			memcpy(cmd->tvc_log, vq->log, sizeof(*cmd->tvc_log) * log_num);
+			cmd->tvc_log_num = log_num;
+		}
+
 		pr_debug("vhost_scsi got command opcode: %#02x, lun: %d\n",
 			 cmd->tvc_cdb[0], cmd->tvc_lun);
 		pr_debug("cmd: %p exp_data_len: %d, prot_bytes: %d data_direction:"
@@ -1269,8 +1304,10 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
 		 */
 		if (ret == -ENXIO)
 			break;
-		else if (ret == -EIO)
+		else if (ret == -EIO) {
 			vhost_scsi_send_bad_target(vs, vq, vc.head, vc.out);
+			vhost_scsi_log_write(vq, vq_log, log_num);
+		}
 	} while (likely(!vhost_exceeds_weight(vq, ++c, 0)));
 out:
 	mutex_unlock(&vq->mutex);
-- 
2.39.3