Re: [RFC] vhost-user public struct refactor (was Re: [PATCH RFC 2/4] vhost: make buf vector for scatter RX) local.

[Thomas Monjalon <thomas.monjalon@6wind.com>]

2016-04-05 13:47, Yuanhan Liu:
> So, I was considering to add vhost-user Tx delayed-copy (or zero copy)
> support recently, which comes to yet another ABI violation, as we need
> add a new field to virtio_memory_regions struct to do guest phys addr
> to host phys addr translation. You may ask, however, that why do we need
> expose virtio_memory_regions struct to users at all?
> 
> You are right, we don't have to. And here is the thing: we exposed way
> too many fields (or even structures) than necessary. Say, vhost_virtqueue
> struct should NOT be exposed to user at all: application just need to
> tell the right queue id to locate a specific queue, and that's all.
> The structure should be defined in an internal header file. With that,
> we could do any changes to it we want, without worrying about that we
> may offense the painful ABI rules.
> 
> Similar changes could be done to virtio_net struct as well, just exposing
> very few fields that are necessary and moving all others to an internal
> structure.
> 
> Huawei then suggested a more radical yet much cleaner one: just exposing
> a virtio_net handle to application, just like the way kernel exposes an
> fd to user for locating a specific file. However, it's more than an ABI
> change; it's also an API change: some fields are referenced by applications,
> such as flags, virt_qp_nb. We could expose some new functions to access
> them though.
> 
> I'd vote for this one, as it sounds very clean to me. This would also
> solve the block issue of this patch. Though it would break OVS, I'm thinking
> that'd be okay, as OVS has dependence on DPDK version: what we need to
> do is just to send few patches to OVS, and let it points to next release,
> say DPDK v16.07. Flavio, please correct me if I'm wrong.
> 
> Thoughts/comments?

Do you plan to send a deprecation notice to change API in 16.07?