Re: [PATCH v4 3/4] vhost-vdpa: uAPI to stop the device

The ioctl adds support for stop the device from userspace.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 drivers/vhost/vdpa.c       | 18 ++++++++++++++++++
 include/uapi/linux/vhost.h | 14 ++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index 32713db5831d..d1d19555c4b7 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c

@@ -478,6 +478,21 @@ static long vhost_vdpa_get_vqs_count(struct vhost_vdpa *v, u32 __user *argp)
 	return 0;
 }
 
+static long vhost_vdpa_stop(struct vhost_vdpa *v, u32 __user *argp)
+{
+	struct vdpa_device *vdpa = v->vdpa;
+	const struct vdpa_config_ops *ops = vdpa->config;
+	int stop;
+
+	if (!ops->stop)
+		return -EOPNOTSUPP;
+
+	if (copy_from_user(&stop, argp, sizeof(stop)))
+		return -EFAULT;
+
+	return ops->stop(vdpa, stop);
+}
+
 static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
 				   void __user *argp)
 {

@@ -650,6 +665,9 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
 	case VHOST_VDPA_GET_VQS_COUNT:
 		r = vhost_vdpa_get_vqs_count(v, argp);
 		break;
+	case VHOST_VDPA_STOP:
+		r = vhost_vdpa_stop(v, argp);
+		break;
 	default:
 		r = vhost_dev_ioctl(&v->vdev, cmd, argp);
 		if (r == -ENOIOCTLCMD)

diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
index cab645d4a645..c7e47b29bf61 100644
--- a/include/uapi/linux/vhost.h
+++ b/include/uapi/linux/vhost.h

@@ -171,4 +171,18 @@
 #define VHOST_VDPA_SET_GROUP_ASID	_IOW(VHOST_VIRTIO, 0x7C, \
 					     struct vhost_vring_state)
 
+/* Stop or resume a device so it does not process virtqueue requests anymore
+ *
+ * After the return of ioctl with stop != 0, the device must finish any
+ * pending operations like in flight requests. It must also preserve all
+ * the necessary state (the virtqueue vring base plus the possible device
+ * specific states) that is required for restoring in the future. The
+ * device must not change its configuration after that point.
+ *
+ * After the return of ioctl with stop == 0, the device can continue
+ * processing buffers as long as typical conditions are met (vq is enabled,
+ * DRIVER_OK status bit is enabled, etc).
+ */
+#define VHOST_VDPA_STOP			_IOW(VHOST_VIRTIO, 0x7D, int)
+
 #endif