tcm_vhost: Add ioctl to get and set events missed flag

Signed-off-by: Asias He <asias@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/vhost/tcm_vhost.c

@@ -1200,8 +1200,11 @@ static long vhost_scsi_ioctl(struct file *f, unsigned int ioctl,
 	struct vhost_scsi_target backend;
 	void __user *argp = (void __user *)arg;
 	u64 __user *featurep = argp;
+	u32 __user *eventsp = argp;
+	u32 events_missed;
 	u64 features;
 	int r, abi_version = VHOST_SCSI_ABI_VERSION;
+	struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT];
 
 	switch (ioctl) {
 	case VHOST_SCSI_SET_ENDPOINT:
@@ -1222,6 +1225,20 @@ static long vhost_scsi_ioctl(struct file *f, unsigned int ioctl,
 		if (copy_to_user(argp, &abi_version, sizeof abi_version))
 			return -EFAULT;
 		return 0;
+	case VHOST_SCSI_SET_EVENTS_MISSED:
+		if (get_user(events_missed, eventsp))
+			return -EFAULT;
+		mutex_lock(&vq->mutex);
+		vs->vs_events_missed = events_missed;
+		mutex_unlock(&vq->mutex);
+		return 0;
+	case VHOST_SCSI_GET_EVENTS_MISSED:
+		mutex_lock(&vq->mutex);
+		events_missed = vs->vs_events_missed;
+		mutex_unlock(&vq->mutex);
+		if (put_user(events_missed, eventsp))
+			return -EFAULT;
+		return 0;
 	case VHOST_GET_FEATURES:
 		features = VHOST_SCSI_FEATURES;
 		if (copy_to_user(featurep, &features, sizeof features))

drivers/vhost/tcm_vhost.h

@@ -123,3 +123,6 @@ struct vhost_scsi_target {
 #define VHOST_SCSI_CLEAR_ENDPOINT _IOW(VHOST_VIRTIO, 0x41, struct vhost_scsi_target)
 /* Changing this breaks userspace. */
 #define VHOST_SCSI_GET_ABI_VERSION _IOW(VHOST_VIRTIO, 0x42, int)
+/* Set and get the events missed flag */
+#define VHOST_SCSI_SET_EVENTS_MISSED _IOW(VHOST_VIRTIO, 0x43, __u32)
+#define VHOST_SCSI_GET_EVENTS_MISSED _IOW(VHOST_VIRTIO, 0x44, __u32)