Existing vhost-user device backends, including vhost-user-scsi and vhost-user-blk, support multiqueue but libvhost-user currently does not advertise this.
VHOST_USER_PROTOCOL_F_MQ enables the VHOST_USER_GET_QUEUE_NUM request needed for a vhost-user master to query the number of queues. For example, QEMU's vhost-user-net master depends on VHOST_USER_PROTOCOL_F_MQ for multiqueue. If you're wondering how any device backend with more than one virtqueue functions today, it's because device types with a fixed number of virtqueues do not require querying the number of queues. Therefore the vhost-user master for vhost-user-input with 2 virtqueues, for example, doesn't actually depend on VHOST_USER_PROTOCOL_F_MQ. It just enables virtqueues 0 and 1 without asking. Let there be multiqueue! Suggested-by: Sebastien Boeuf <sebastien.bo...@intel.com> Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com> Reviewed-by: Marc-André Lureau <marcandre.lur...@redhat.com> --- contrib/libvhost-user/libvhost-user.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/contrib/libvhost-user/libvhost-user.c b/contrib/libvhost-user/libvhost-user.c index 90bea856dd..4b36e35a82 100644 --- a/contrib/libvhost-user/libvhost-user.c +++ b/contrib/libvhost-user/libvhost-user.c @@ -1160,7 +1160,8 @@ vu_set_vring_err_exec(VuDev *dev, VhostUserMsg *vmsg) static bool vu_get_protocol_features_exec(VuDev *dev, VhostUserMsg *vmsg) { - uint64_t features = 1ULL << VHOST_USER_PROTOCOL_F_LOG_SHMFD | + uint64_t features = 1ULL << VHOST_USER_PROTOCOL_F_MQ | + 1ULL << VHOST_USER_PROTOCOL_F_LOG_SHMFD | 1ULL << VHOST_USER_PROTOCOL_F_SLAVE_REQ | 1ULL << VHOST_USER_PROTOCOL_F_HOST_NOTIFIER | 1ULL << VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD; @@ -1200,8 +1201,8 @@ vu_set_protocol_features_exec(VuDev *dev, VhostUserMsg *vmsg) static bool vu_get_queue_num_exec(VuDev *dev, VhostUserMsg *vmsg) { - DPRINT("Function %s() not implemented yet.\n", __func__); - return false; + vmsg_set_reply_u64(vmsg, dev->max_queues); + return true; } static bool -- 2.21.0