vhost-user-blk: simplify and fix vhost_user_blk_handle_config_change

Let's not care about what was changed and update the whole config,
reasons:

1. config->geometry should be updated together with capacity, so we fix
   a bug.

2. Vhost-user protocol doesn't say anything about config change
   limitation. Silent ignore of changes doesn't seem to be correct.

3. vhost-user-vsock reads the whole config

4. on realize we don't do any checks on retrieved config, so no reason
   to care here

Comment "valid for resize only" exists since introduction the whole
hw/block/vhost-user-blk.c in commit
   00343e4
    "vhost-user-blk: introduce a new vhost-user-blk host device",
seems it was just an extra limitation.

Also, let's notify guest unconditionally:

1. So does vhost-user-vsock

2. We are going to reuse the functionality in new cases when we do want
   to notify the guest unconditionally. So, no reason to create extra
   branches in the logic.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Acked-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Message-Id: <20240329183758.3360733-2-vsementsov@yandex-team.ru>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/block/vhost-user-blk.c

@@ -91,7 +91,6 @@ static void vhost_user_blk_set_config(VirtIODevice *vdev, const uint8_t *config)
 static int vhost_user_blk_handle_config_change(struct vhost_dev *dev)
 {
     int ret;
-    struct virtio_blk_config blkcfg;
     VirtIODevice *vdev = dev->vdev;
     VHostUserBlk *s = VHOST_USER_BLK(dev->vdev);
     Error *local_err = NULL;
@@ -100,19 +99,15 @@ static int vhost_user_blk_handle_config_change(struct vhost_dev *dev)
         return 0;
     }
 
-    ret = vhost_dev_get_config(dev, (uint8_t *)&blkcfg,
+    ret = vhost_dev_get_config(dev, (uint8_t *)&s->blkcfg,
                                vdev->config_len, &local_err);
     if (ret < 0) {
         error_report_err(local_err);
         return ret;
     }
 
-    /* valid for resize only */
-    if (blkcfg.capacity != s->blkcfg.capacity) {
-        s->blkcfg.capacity = blkcfg.capacity;
-        memcpy(dev->vdev->config, &s->blkcfg, vdev->config_len);
-        virtio_notify_config(dev->vdev);
-    }
+    memcpy(dev->vdev->config, &s->blkcfg, vdev->config_len);
+    virtio_notify_config(dev->vdev);
 
     return 0;
 }