Weird vhost-user-blk features

[Feng Li]

When I'm testing the vhost-user-blk, and I found the features bits in
guest os are not the same as the setting in vhost backend.
After digging into the details, I found there are two different
features set path.
One is the vhost-user socket path VHOST_USER_GET_FEATURES, the another is:

220 static uint64_t vhost_user_blk_get_features(VirtIODevice *vdev,
221                                             uint64_t features,
222                                             Error **errp)
223 {
224     VHostUserBlk *s = VHOST_USER_BLK(vdev);
225     uint64_t get_features;
226
227     /* Turn on pre-defined features */
228     virtio_add_feature(&features, VIRTIO_BLK_F_SEG_MAX);
229     virtio_add_feature(&features, VIRTIO_BLK_F_GEOMETRY);
230     virtio_add_feature(&features, VIRTIO_BLK_F_TOPOLOGY);
231     virtio_add_feature(&features, VIRTIO_BLK_F_BLK_SIZE);
232     virtio_add_feature(&features, VIRTIO_BLK_F_FLUSH);
233
234     if (s->config_wce) {
235         virtio_add_feature(&features, VIRTIO_BLK_F_CONFIG_WCE);
236     }
237     if (s->config_ro) {
238         virtio_add_feature(&features, VIRTIO_BLK_F_RO);
239     }
240     if (s->num_queues > 1) {
241         virtio_add_feature(&features, VIRTIO_BLK_F_MQ);
242     }
243
244     get_features = vhost_get_features(&s->dev, user_feature_bits, features);
245
246     return get_features;
247 }

This set is the last one, so whatever features I have set in vhost
backend still doesn't work.
For example, I set device features to 0x754005646, after negotiation,
the device features are 0x110000644.
This issue is definitely from Qemu, not the vhost backend, and linux kernel.
Looks like this code is copied from virtio-blk.c, it's not right.

[root@node1 13:17:29 ~]$print_features 0x110000644
2: 1
6: 1
9: 1
10: 1
28: 1
32: 1


[root@node1 13:17:43 ~]$print_features 0x754005646
1: 1
2: 1
6: 1
9: 1
10: 1
12: 1
14: 1
26: 1
28: 1
30: 1
32: 1
33: 1
34: 1