From a9a5c473d25d83bcdad27d97e5fb451950ee894a Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Fri, 29 May 2020 17:13:38 +0100 Subject: [PATCH] libvhost-user: advertise vring features MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Cc: Jason Wang Cc: Michael S. Tsirkin Signed-off-by: Stefan Hajnoczi Message-Id: <20200529161338.456017-1-stefanha@redhat.com> Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin Reviewed-by: Marc-André Lureau --- 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;