From: Longpeng <longpeng2@huawei.com>
Date: Tue, 15 Mar 2022 11:25:51 +0800
Subject: vdpa: support exposing the config size to userspace
Patch-mainline: v5.18-rc1
Git-commit: a61280ddddaa45f95b60dd54c05f8e0e5b6810b7
References: jsc#PED-1549

- 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>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/vhost/vdpa.c       |   17 +++++++++++++++++
 include/linux/vdpa.h       |    3 ++-
 include/uapi/linux/vhost.h |    4 ++++
 3 files changed, 23 insertions(+), 1 deletion(-)

--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -358,6 +358,20 @@ static long vhost_vdpa_get_iova_range(st
 	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(st
 	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)
--- 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
--- 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