Re: [dpdk-dev] [PATCH v5 1/3] vhost: Add callback and private data for vhost PMD

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

2015-12-23 10:44, Yuanhan Liu:
> On Tue, Dec 22, 2015 at 01:38:29AM -0800, Rich Lane wrote:
> > On Mon, Dec 21, 2015 at 9:47 PM, Yuanhan Liu <yuanhan.liu@linux.intel.com>
> > wrote:
> > 
> >     On Mon, Dec 21, 2015 at 08:47:28PM -0800, Rich Lane wrote:
> >     > The queue state change callback is the one new API that needs to be
> >     > added because
> >     > normal NICs don't have this behavior.
> > 
> >     Again I'd ask, will vring_state_changed() be enough, when above issues
> >     are resolved: vring_state_changed() will be invoked at new_device()/
> >     destroy_device(), and of course, ethtool change?
> > 
> > 
> > It would be sufficient. It is not a great API though, because it requires the
> > application to do the conversion from struct virtio_net to a DPDK port number,
> > and from a virtqueue index to a DPDK queue id and direction. Also, the current
> > implementation often makes this callback when the vring state has not actually
> > changed (enabled -> enabled and disabled -> disabled).
> > 
> > If you're asking about using vring_state_changed() _instead_ of the link status
> > event and rte_eth_dev_socket_id(),
> 
> No, I like the idea of link status event and rte_eth_dev_socket_id();
> I was just wondering why a new API is needed. Both Tetsuya and I
> were thinking to leverage the link status event to represent the
> queue stats change (triggered by vring_state_changed()) as well,
> so that we don't need to introduce another eth event. However, I'd
> agree that it's better if we could have a new dedicate event.
> 
> Thomas, here is some background for you. For vhost pmd and linux
> virtio-net combo, the queue can be dynamically changed by ethtool,
> therefore, the application wishes to have another eth event, say
> RTE_ETH_EVENT_QUEUE_STATE_CHANGE, so that the application can
> add/remove corresponding queue to the datapath when that happens.
> What do you think of that?

Yes it is an event. So I don't understand the question.
What may be better than a specific rte_eth_event_type?