[PATCH 6/9] vhost-scsi: log event queue write descriptors

[Dongli Zhang]

Log write descriptors for the event queue, leveraging vhost_get_vq_desc()
to retrieve the array of write descriptors to obtain the log buffer.

There is only one path for event queue.

Suggested-by: Joao Martins <joao.m.mart...@oracle.com>
Signed-off-by: Dongli Zhang <dongli.zh...@oracle.com>
---
 drivers/vhost/scsi.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 21c2d07b806a..40268b88f470 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -498,6 +498,8 @@ vhost_scsi_do_evt_work(struct vhost_scsi *vs, struct 
vhost_scsi_evt *evt)
        struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;
        struct virtio_scsi_event *event = &evt->event;
        struct virtio_scsi_event __user *eventp;
+       struct vhost_log *vq_log;
+       unsigned int log_num;
        unsigned out, in;
        int head, ret;
 
@@ -508,9 +510,19 @@ vhost_scsi_do_evt_work(struct vhost_scsi *vs, struct 
vhost_scsi_evt *evt)
 
 again:
        vhost_disable_notify(&vs->dev, vq);
+
+       vq_log = unlikely(vhost_has_feature(vq, VHOST_F_LOG_ALL)) ?
+               vq->log : NULL;
+
+       /*
+        * Reset 'log_num' since vhost_get_vq_desc() may reset it only
+        * after certain condition checks.
+        */
+       log_num = 0;
+
        head = vhost_get_vq_desc(vq, vq->iov,
                        ARRAY_SIZE(vq->iov), &out, &in,
-                       NULL, NULL);
+                       vq_log, &log_num);
        if (head < 0) {
                vs->vs_events_missed = true;
                return;
@@ -540,6 +552,8 @@ vhost_scsi_do_evt_work(struct vhost_scsi *vs, struct 
vhost_scsi_evt *evt)
                vhost_add_used_and_signal(&vs->dev, vq, head, 0);
        else
                vq_err(vq, "Faulted on vhost_scsi_send_event\n");
+
+       vhost_scsi_log_write(vq, vq_log, log_num);
 }
 
 static void vhost_scsi_complete_events(struct vhost_scsi *vs, bool drop)
-- 
2.39.3