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Date:   Sun, 7 Jun 2020 10:11:46 -0400
From:   "Michael S. Tsirkin" <mst@redhat.com>
To:     linux-kernel@vger.kernel.org
Cc:     kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
        netdev@vger.kernel.org, Jason Wang <jasowang@redhat.com>,
        eperezma@redhat.com, Paolo Bonzini <pbonzini@redhat.com>,
        Stefan Hajnoczi <stefanha@redhat.com>
Subject: [PATCH RFC v5 11/13] vhost/scsi: switch to buf APIs
Message-ID: <20200607141057.704085-12-mst@redhat.com>
References: <20200607141057.704085-1-mst@redhat.com>
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In-Reply-To: <20200607141057.704085-1-mst@redhat.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Switch to buf APIs. Doing this exposes a spec violation in vhost scsi:
all used bufs are marked with length 0.
Fix that is left for another day.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 drivers/vhost/scsi.c | 73 ++++++++++++++++++++++++++------------------
 1 file changed, 44 insertions(+), 29 deletions(-)

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 0cbaa0b3893d..a5cdd4c01a3a 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -71,8 +71,8 @@ struct vhost_scsi_inflight {
 };
 
 struct vhost_scsi_cmd {
-	/* Descriptor from vhost_get_vq_desc() for virt_queue segment */
-	int tvc_vq_desc;
+	/* Descriptor from vhost_get_avail_buf() for virt_queue segment */
+	struct vhost_buf tvc_vq_desc;
 	/* virtio-scsi initiator task attribute */
 	int tvc_task_attr;
 	/* virtio-scsi response incoming iovecs */
@@ -213,7 +213,7 @@ struct vhost_scsi {
  * Context for processing request and control queue operations.
  */
 struct vhost_scsi_ctx {
-	int head;
+	struct vhost_buf buf;
 	unsigned int out, in;
 	size_t req_size, rsp_size;
 	size_t out_size, in_size;
@@ -443,6 +443,20 @@ static int vhost_scsi_check_stop_free(struct se_cmd *se_cmd)
 	return target_put_sess_cmd(se_cmd);
 }
 
+/* Signal to guest that request finished with no input buffer. */
+/* TODO calling this when writing into buffer and most likely a bug */
+static void vhost_scsi_signal_noinput(struct vhost_dev *vdev,
+				      struct vhost_virtqueue *vq,
+				      struct vhost_buf *bufp)
+{
+	struct vhost_buf buf = *bufp;
+
+	buf.in_len = 0;
+	vhost_put_used_buf(vq, &buf);
+	vhost_signal(vdev, vq);
+}
+
+
 static void
 vhost_scsi_do_evt_work(struct vhost_scsi *vs, struct vhost_scsi_evt *evt)
 {
@@ -450,7 +464,8 @@ vhost_scsi_do_evt_work(struct vhost_scsi *vs, struct vhost_scsi_evt *evt)
 	struct virtio_scsi_event *event = &evt->event;
 	struct virtio_scsi_event __user *eventp;
 	unsigned out, in;
-	int head, ret;
+	struct vhost_buf buf;
+	int ret;
 
 	if (!vhost_vq_get_backend(vq)) {
 		vs->vs_events_missed = true;
@@ -459,14 +474,14 @@ vhost_scsi_do_evt_work(struct vhost_scsi *vs, struct vhost_scsi_evt *evt)
 
 again:
 	vhost_disable_notify(&vs->dev, vq);
-	head = vhost_get_vq_desc(vq, vq->iov,
-			ARRAY_SIZE(vq->iov), &out, &in,
-			NULL, NULL);
-	if (head < 0) {
+	ret = vhost_get_avail_buf(vq, &buf,
+				  vq->iov, ARRAY_SIZE(vq->iov), &out, &in,
+				  NULL, NULL);
+	if (ret < 0) {
 		vs->vs_events_missed = true;
 		return;
 	}
-	if (head == vq->num) {
+	if (!ret) {
 		if (vhost_enable_notify(&vs->dev, vq))
 			goto again;
 		vs->vs_events_missed = true;
@@ -488,7 +503,7 @@ vhost_scsi_do_evt_work(struct vhost_scsi *vs, struct vhost_scsi_evt *evt)
 	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);
+		vhost_scsi_signal_noinput(&vs->dev, vq, &buf);
 	else
 		vq_err(vq, "Faulted on vhost_scsi_send_event\n");
 }
@@ -549,7 +564,7 @@ static void vhost_scsi_complete_cmd_work(struct vhost_work *work)
 		ret = copy_to_iter(&v_rsp, sizeof(v_rsp), &iov_iter);
 		if (likely(ret == sizeof(v_rsp))) {
 			struct vhost_scsi_virtqueue *q;
-			vhost_add_used(cmd->tvc_vq, cmd->tvc_vq_desc, 0);
+			vhost_put_used_buf(cmd->tvc_vq, &cmd->tvc_vq_desc);
 			q = container_of(cmd->tvc_vq, struct vhost_scsi_virtqueue, vq);
 			vq = q - vs->vqs;
 			__set_bit(vq, signal);
@@ -793,7 +808,7 @@ static void vhost_scsi_submission_work(struct work_struct *work)
 static void
 vhost_scsi_send_bad_target(struct vhost_scsi *vs,
 			   struct vhost_virtqueue *vq,
-			   int head, unsigned out)
+			   struct vhost_buf *buf, unsigned out)
 {
 	struct virtio_scsi_cmd_resp __user *resp;
 	struct virtio_scsi_cmd_resp rsp;
@@ -804,7 +819,7 @@ vhost_scsi_send_bad_target(struct vhost_scsi *vs,
 	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);
+		vhost_scsi_signal_noinput(&vs->dev, vq, buf);
 	else
 		pr_err("Faulted on virtio_scsi_cmd_resp\n");
 }
@@ -813,21 +828,21 @@ static int
 vhost_scsi_get_desc(struct vhost_scsi *vs, struct vhost_virtqueue *vq,
 		    struct vhost_scsi_ctx *vc)
 {
-	int ret = -ENXIO;
+	int r, ret = -ENXIO;
 
-	vc->head = vhost_get_vq_desc(vq, vq->iov,
-				     ARRAY_SIZE(vq->iov), &vc->out, &vc->in,
-				     NULL, NULL);
+	r = vhost_get_avail_buf(vq, &vc->buf,
+				vq->iov, ARRAY_SIZE(vq->iov), &vc->out, &vc->in,
+				NULL, NULL);
 
-	pr_debug("vhost_get_vq_desc: head: %d, out: %u in: %u\n",
-		 vc->head, vc->out, vc->in);
+	pr_debug("vhost_get_avail_buf: buf: %d, out: %u in: %u\n",
+		 vc->buf.id, vc->out, vc->in);
 
 	/* On error, stop handling until the next kick. */
-	if (unlikely(vc->head < 0))
+	if (unlikely(r < 0))
 		goto done;
 
 	/* Nothing new?  Wait for eventfd to tell us they refilled. */
-	if (vc->head == vq->num) {
+	if (!r) {
 		if (unlikely(vhost_enable_notify(&vs->dev, vq))) {
 			vhost_disable_notify(&vs->dev, vq);
 			ret = -EAGAIN;
@@ -1093,11 +1108,11 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
 			}
 		}
 		/*
-		 * Save the descriptor from vhost_get_vq_desc() to be used to
+		 * Save the descriptor from vhost_get_avail_buf() to be used to
 		 * complete the virtio-scsi request in TCM callback context via
 		 * vhost_scsi_queue_data_in() and vhost_scsi_queue_status()
 		 */
-		cmd->tvc_vq_desc = vc.head;
+		cmd->tvc_vq_desc = vc.buf;
 		/*
 		 * Dispatch cmd descriptor for cmwq execution in process
 		 * context provided by vhost_scsi_workqueue.  This also ensures
@@ -1117,7 +1132,7 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
 		if (ret == -ENXIO)
 			break;
 		else if (ret == -EIO)
-			vhost_scsi_send_bad_target(vs, vq, vc.head, vc.out);
+			vhost_scsi_send_bad_target(vs, vq, &vc.buf, vc.out);
 	} while (likely(!vhost_exceeds_weight(vq, ++c, 0)));
 out:
 	mutex_unlock(&vq->mutex);
@@ -1139,9 +1154,9 @@ vhost_scsi_send_tmf_reject(struct vhost_scsi *vs,
 	iov_iter_init(&iov_iter, READ, &vq->iov[vc->out], vc->in, sizeof(rsp));
 
 	ret = copy_to_iter(&rsp, sizeof(rsp), &iov_iter);
-	if (likely(ret == sizeof(rsp)))
-		vhost_add_used_and_signal(&vs->dev, vq, vc->head, 0);
-	else
+	if (likely(ret == sizeof(rsp))) {
+		vhost_scsi_signal_noinput(&vs->dev, vq, &vc->buf);
+	} else
 		pr_err("Faulted on virtio_scsi_ctrl_tmf_resp\n");
 }
 
@@ -1162,7 +1177,7 @@ vhost_scsi_send_an_resp(struct vhost_scsi *vs,
 
 	ret = copy_to_iter(&rsp, sizeof(rsp), &iov_iter);
 	if (likely(ret == sizeof(rsp)))
-		vhost_add_used_and_signal(&vs->dev, vq, vc->head, 0);
+		vhost_scsi_signal_noinput(&vs->dev, vq, &vc->buf);
 	else
 		pr_err("Faulted on virtio_scsi_ctrl_an_resp\n");
 }
@@ -1269,7 +1284,7 @@ vhost_scsi_ctl_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
 		if (ret == -ENXIO)
 			break;
 		else if (ret == -EIO)
-			vhost_scsi_send_bad_target(vs, vq, vc.head, vc.out);
+			vhost_scsi_send_bad_target(vs, vq, &vc.buf, vc.out);
 	} while (likely(!vhost_exceeds_weight(vq, ++c, 0)));
 out:
 	mutex_unlock(&vq->mutex);
-- 
MST