[PATCH v2 1/2] vdpa: support exposing the config size to userspace

["Longpeng(Mike)" <longpeng2@huawei.com>]

From: Longpeng <longpeng2@huawei.com>

- GET_CONFIG_SIZE: return the size of the virtio config space.

The size contains the fields which are conditional on feature
bits.

Signed-off-by: Longpeng <longpeng2@huawei.com>
---
 drivers/vhost/vdpa.c       | 17 +++++++++++++++++
 include/linux/vdpa.h       |  3 ++-
 include/uapi/linux/vhost.h |  4 ++++
 3 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index ec5249e..605c7ae 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -355,6 +355,20 @@ static long vhost_vdpa_get_iova_range(struct vhost_vdpa *v, u32 __user *argp)
 	return 0;
 }
 
+static long vhost_vdpa_get_config_size(struct vhost_vdpa *v, u32 __user *argp)
+{
+	struct vdpa_device *vdpa = v->vdpa;
+	const struct vdpa_config_ops *ops = vdpa->config;
+	u32 size;
+
+	size = ops->get_config_size(vdpa);
+
+	if (copy_to_user(argp, &size, sizeof(size)))
+		return -EFAULT;
+
+	return 0;
+}
+
 static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
 				   void __user *argp)
 {
@@ -492,6 +506,9 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
 	case VHOST_VDPA_GET_IOVA_RANGE:
 		r = vhost_vdpa_get_iova_range(v, argp);
 		break;
+	case VHOST_VDPA_GET_CONFIG_SIZE:
+		r = vhost_vdpa_get_config_size(v, argp);
+		break;
 	default:
 		r = vhost_dev_ioctl(&v->vdev, cmd, argp);
 		if (r == -ENOIOCTLCMD)
diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
index 721089b..a526919 100644
--- a/include/linux/vdpa.h
+++ b/include/linux/vdpa.h
@@ -207,7 +207,8 @@ struct vdpa_map_file {
  * @reset:			Reset device
  *				@vdev: vdpa device
  *				Returns integer: success (0) or error (< 0)
- * @get_config_size:		Get the size of the configuration space
+ * @get_config_size:		Get the size of the configuration space includes
+ *				fields that are conditional on feature bits.
  *				@vdev: vdpa device
  *				Returns size_t: configuration size
  * @get_config:			Read from device specific configuration space
diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
index c998860..bc74e95 100644
--- a/include/uapi/linux/vhost.h
+++ b/include/uapi/linux/vhost.h
@@ -150,4 +150,8 @@
 /* Get the valid iova range */
 #define VHOST_VDPA_GET_IOVA_RANGE	_IOR(VHOST_VIRTIO, 0x78, \
 					     struct vhost_vdpa_iova_range)
+
+/* Get the config size */
+#define VHOST_VDPA_GET_CONFIG_SIZE	_IOR(VHOST_VIRTIO, 0x79, __u32)
+
 #endif
-- 
1.8.3.1