@@ -495,6 +495,16 @@ static bool
vu_get_features_exec(VuDev *dev, VhostUserMsg *vmsg)
{
vmsg->payload.u64 =
+ /*
+ * The following VIRTIO feature bits are supported by our virtqueue
+ * implementation:
+ */
+ 1ULL << VIRTIO_F_NOTIFY_ON_EMPTY |
+ 1ULL << VIRTIO_RING_F_INDIRECT_DESC |
+ 1ULL << VIRTIO_RING_F_EVENT_IDX |
+ 1ULL << VIRTIO_F_VERSION_1 |
+
+ /* vhost-user feature bits */
1ULL << VHOST_F_LOG_ALL |
1ULL << VHOST_USER_F_PROTOCOL_FEATURES;
@@ -382,9 +382,7 @@ vub_get_features(VuDev *dev)
1ull << VIRTIO_BLK_F_DISCARD |
1ull << VIRTIO_BLK_F_WRITE_ZEROES |
#endif
- 1ull << VIRTIO_BLK_F_CONFIG_WCE |
- 1ull << VIRTIO_F_VERSION_1 |
- 1ull << VHOST_USER_F_PROTOCOL_FEATURES;
+ 1ull << VIRTIO_BLK_F_CONFIG_WCE;
if (vdev_blk->enable_ro) {
features |= 1ull << VIRTIO_BLK_F_RO;
libvhost-user implements several vring features without advertising them. There is no way for the vhost-user master to detect support for these features. Things more or less work today because QEMU assumes the vhost-user backend always implements certain feature bits like VIRTIO_RING_F_EVENT_IDX. This is not documented anywhere. This patch explicitly advertises features implemented in libvhost-user so that the vhost-user master does not need to make undocumented assumptions. Feature bits that libvhost-user now advertises can be removed from vhost-user-blk.c. Devices should not be responsible for advertising vring feature bits, that is libvhost-user's job. Cc: Marc-André Lureau <marcandre.lureau@redhat.com> Cc: Jason Wang <jasowang@redhat.com> Cc: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> --- I have tested make check and virtiofsd. --- contrib/libvhost-user/libvhost-user.c | 10 ++++++++++ contrib/vhost-user-blk/vhost-user-blk.c | 4 +--- 2 files changed, 11 insertions(+), 3 deletions(-)