From: Stefan Hajnoczi <stefa...@redhat.com>
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.lur...@redhat.com>
Cc: Jason Wang <jasow...@redhat.com>
Cc: Michael S. Tsirkin <m...@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
Message-Id: <20200529161338.456017-1-stefa...@redhat.com>
Reviewed-by: Michael S. Tsirkin <m...@redhat.com>
Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lur...@redhat.com>
---
contrib/libvhost-user/libvhost-user.c | 10 ++++++++++
contrib/vhost-user-blk/vhost-user-blk.c | 4 +---
2 files changed, 11 insertions(+), 3 deletions(-)
diff --git a/contrib/libvhost-user/libvhost-user.c
b/contrib/libvhost-user/libvhost-user.c
index b1e607298c..d315db1396 100644
--- a/contrib/libvhost-user/libvhost-user.c
+++ b/contrib/libvhost-user/libvhost-user.c
@@ -498,6 +498,16 @@ 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;
diff --git a/contrib/vhost-user-blk/vhost-user-blk.c
b/contrib/vhost-user-blk/vhost-user-blk.c
index 6fd91c7e99..25eccd02b5 100644
--- a/contrib/vhost-user-blk/vhost-user-blk.c
+++ b/contrib/vhost-user-blk/vhost-user-blk.c
@@ -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;
--
MST
