[5.10,05/29] vdpa_sim: add get_config callback in vdpasim_dev_attr

--- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
@@ -69,9 +69,12 @@  static u64 vdpasim_features = (1ULL << V
 			      (1ULL << VIRTIO_F_ACCESS_PLATFORM) |
 			      (1ULL << VIRTIO_NET_F_MAC);
 
+struct vdpasim;
+
 struct vdpasim_dev_attr {
 	size_t config_size;
 	int nvqs;
+	void (*get_config)(struct vdpasim *vdpasim, void *config);
 };
 
 /* State of each vdpasim device */
@@ -524,8 +527,6 @@  static u64 vdpasim_get_features(struct v
 static int vdpasim_set_features(struct vdpa_device *vdpa, u64 features)
 {
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
-	struct virtio_net_config *config =
-		(struct virtio_net_config *)vdpasim->config;
 
 	/* DMA mapping must be done by driver */
 	if (!(features & (1ULL << VIRTIO_F_ACCESS_PLATFORM)))
@@ -533,16 +534,6 @@  static int vdpasim_set_features(struct v
 
 	vdpasim->features = features & vdpasim_features;
 
-	/* We generally only know whether guest is using the legacy interface
-	 * here, so generally that's the earliest we can set config fields.
-	 * Note: We actually require VIRTIO_F_ACCESS_PLATFORM above which
-	 * implies VIRTIO_F_VERSION_1, but let's not try to be clever here.
-	 */
-
-	config->mtu = cpu_to_vdpasim16(vdpasim, 1500);
-	config->status = cpu_to_vdpasim16(vdpasim, VIRTIO_NET_S_LINK_UP);
-	memcpy(config->mac, macaddr_buf, ETH_ALEN);
-
 	return 0;
 }
 
@@ -595,8 +586,13 @@  static void vdpasim_get_config(struct vd
 {
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 
-	if (offset + len < vdpasim->dev_attr.config_size)
-		memcpy(buf, vdpasim->config + offset, len);
+	if (offset + len > vdpasim->dev_attr.config_size)
+		return;
+
+	if (vdpasim->dev_attr.get_config)
+		vdpasim->dev_attr.get_config(vdpasim, vdpasim->config);
+
+	memcpy(buf, vdpasim->config + offset, len);
 }
 
 static void vdpasim_set_config(struct vdpa_device *vdpa, unsigned int offset,
@@ -739,12 +735,23 @@  static const struct vdpa_config_ops vdpa
 	.free                   = vdpasim_free,
 };
 
+static void vdpasim_net_get_config(struct vdpasim *vdpasim, void *config)
+{
+	struct virtio_net_config *net_config =
+		(struct virtio_net_config *)config;
+
+	net_config->mtu = cpu_to_vdpasim16(vdpasim, 1500);
+	net_config->status = cpu_to_vdpasim16(vdpasim, VIRTIO_NET_S_LINK_UP);
+	memcpy(net_config->mac, macaddr_buf, ETH_ALEN);
+}
+
 static int __init vdpasim_dev_init(void)
 {
 	struct vdpasim_dev_attr dev_attr = {};
 
 	dev_attr.nvqs = VDPASIM_VQ_NUM;
 	dev_attr.config_size = sizeof(struct virtio_net_config);
+	dev_attr.get_config = vdpasim_net_get_config;
 
 	vdpasim_dev = vdpasim_create(&dev_attr);