On 01/07/2020 11:28, Stokes, Ian wrote: > Hi All, > > While completing validation work for DPDK 18.11.9 and 19.11.3 it was > found that zero-copy for vhostuserclient devices is no longer possible. > Please see commit below from 18.11.9 (note this patch is also in DPDK > 19.11.3) >
Thanks catching this in your validation, it almost certainly wouldn't have been caught otherwise. > > commit 81e025d7ed6a802845909df6fb90505508dc0fbf > Author: Xuan Ding <[email protected]> > Date: Wed Apr 29 02:59:46 2020 +0000 > > vhost: prevent zero-copy with incompatible client mode > > [ upstream commit 715070ea10e6da1169deef2a3ea77ae934b4c333 ] > > In server mode, virtio-user inits under the assumption that vhost-user > supports a list of features. However, this could be problematic when > in_order feature is negotiated but not supported by vhost-user when > enables dequeue_zero_copy later. > > Add handling when vhost-user enables dequeue_zero_copy as client. > > OVS only supports zero-copy to date as an experimental feature with > dpdkvhostuserclient port types. > > We were aiming to update the validated DPDK versions as follows and > recommend them as minimum versions due to the inclusion of CSE fixes. > > OVS 2.11 -> 18.11.6 -> 18.11.9 > OVS 2.12 -> 18.11.6 -> 18.11.9 > OVS 2.13 -> 19.11.0 -> 19.11.3 > OVS Master -> 19.11.0 -> 19.11.3 > > However recommending these DPDK version will trigger the dpdk zero copy > functionality break in OVS. > 18.11.9 is not released yet, so at least for it, I think we could replace that patch(es) with a warning. That is not removing any functionality or causing a regression for users of earlier 18.11.x or OVS 2.11/2.12, but it is letting them know there may be an issue. if (vsocket->dequeue_zero_copy) { if ((flags & RTE_VHOST_USER_CLIENT) != 0) { - RTE_LOG(ERR, VHOST_CONFIG, - "error: zero copy is incompatible with vhost client mode\n"); - ret = -1; - goto out_mutex; + RTE_LOG(WARNING, VHOST_CONFIG, + "zero copy may be incompatible with vhost client mode\n"); } > What are peoples thoughts here on how to proceed? > Are people aware if the feature is used in deployments to date? If not, > as it's experimental is it something that should be removed? > > I'm aware that there is discussion ongoing about tagging for 2.13.1, > 2.12.1, 2.11.3 releases, I'm thinking the vhost zero copy issue should > be resolved within that time frame and before we update the recommended > DPDK versions. > > BR > Ian > > _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
