Re: [libvirt] [dpdk-dev] dpdk/vpp and cross-version migration for vhost
2016-11-28 16:28, Maxime Coquelin:
On 11/24/2016 04:24 PM, Kavanagh, Mark B wrote:
> DPDK v16.04 added support for vHost User TSO; as such, by default,
> TSO is advertised to guest devices as an available feature during
> feature negotiation with QEMU.
> However, while the vHost user backend sets up the majority of the
> mbuf fields that are required for TSO, there is still a reliance
> on the associated DPDK application (i.e. in this case OvS-DPDK)
> to set the remaining flags and/or offsets.
> Since OvS-DPDK doesn't currently provide that functionality, it is
> necessary to explicitly disable TSO; otherwise, undefined behaviour
> will ensue.
Thanks Mark for the clarification.
In this case, maybe we could add a DPDK build option to disable Vhost's
TSO support, that would be selected for OVS packages?
Why do you prefer a build-time option rather than the run-time config
with rte_vhost_feature_disable()? Because we need to lock the features?
Reminder: build-time configuration options are forbidden in DPDK for
such usage. It would prevent other applications from using the feature
in a given distribution, just because it is not implemented in OVS.
Does that sound reasonable?
Maybe I'm missing something but I feel it is more reasonnable to implement
the missing code in OVS.
If something is missing in DPDK, do not hesitate to request or add more
helper functions.