vdpa: support exposing the config size to userspace

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

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

Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Longpeng <longpeng2@huawei.com>
Link: https://lore.kernel.org/r/20220315032553.455-2-longpeng2@huawei.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index 05f5fd2..0437572 100644 (file)
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -358,6 +358,20 @@ 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)
 {
@@ -495,6 +509,9 @@ 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 (file)
--- 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 (file)
--- 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