On Wed, Sep 21, 2016 at 03:07:51PM +0200, Thomas Monjalon wrote:
> 2016-09-18 16:27, Yuanhan Liu:
> > On Wed, Sep 14, 2016 at 10:35:53AM +0200, Thomas Monjalon wrote:
> > > 2016-09-14 15:21, Yuanhan Liu:
> > > > On Wed, Sep 14, 2016 at 09:10:48AM +0200, Thomas Monjalon wrote:
> > > > > 2016-09-14 12:43, Yuanhan Liu:
> > > > > > On Tue, Sep 13, 2016 at 05:10:09PM +0200, Thomas Monjalon wrote:
> > > > > > > 2016-09-13 14:47, Ciara Loftus:
> > > > > > > > In some cases when using the vHost PMD, certain vHost library
> > > > > > > > functions
> > > > > > > > may still need to be accessed. One such example is the
> > > > > > > > rte_vhost_get_queue_num function which returns the number of
> > > > > > > > virtqueues
> > > > > > > > reported by the guest - information which is not exposed by the
> > > > > > > > PMD.
> > > > > > > >
> > > > > > > > This commit introduces a new rte_eth_vhost function that
> > > > > > > > returns the
> > > > > > > > 'vid' associated with a given port id. This allows the PMD user
> > > > > > > > to call
> > > > > > > > vHost library functions which require the 'vid' value.
> > > > > > >
> > > > > > > I think we should not add any API to the PMDs.
> > > > > >
> > > > > > In general, I agree with you.
> > > > > >
> > > > > > > Maybe you are looking for a generic API in ethdev.
> > > > > >
> > > > > > But maybe it's a bit hard to define a "right" generic API here. For
> > > > > > this
> > > > > > case, the generic API I can think of could be:
> > > > > >
> > > > > > - an API to get queue num, like rte_eth_get_queue_enabled_num
> > > > > > I barely know NIC pmd drivers, but I doubt it's useful/meaningful
> > > > > > for them.
> > > > > >
> > > > > > - an API to get a PMD driver private (or specific) data.
> > > > > > For vhost-pmd, it's vid. Again, I don't know what it could be for
> > > > > > other nic
> > > > > > drivers.
> > > > > >
> > > > > > This one may be a better option here, because it expose a key
> > > > > > field to
> > > > > > the application, vid, with which the application can invoke more
> > > > > > vhost
> > > > > > APIs. And apparently, it's not feasible to try to define a
> > > > > > generic API
> > > > > > for some (if not each) vhost APIs.
> > > > >
> > > > > There could be a similar need in other PMD.
> > > > > If we can get an opaque identifier of the device which is not the
> > > > > port id,
> > > > > we could call some specific functions of the driver not implemented in
> > > > > the generic ethdev API.
> > > >
> > > > That means you have to add/export the PMD API first. Isn't it against
> > > > what
> > > > you are proposing -- "I think we should not add any API to the PMDs" ;)
> > >
> > > Yes you are totally right :)
> > > Except that in vhost case, we would not have any API in the PMD.
> > > But it would allow to have some specific API in other PMDs for the
> > > features
> > > which do not fit in a generic API.
> >
> > So, does that mean you are okay with this patch now? I mean, okay to
> > introduce
> > a vhost PMD API?
>
> It means I would be in favor of introducing API in drivers for very specific
> features.
> In this case, I am not sure that retrieving an internal id is very specific.
It's not, instead, it's very generic. The "internal id" is actually the
public interface to vhost-user application, like "fd" to file APIs.
Instead of introducing a few specific wrappers/APIs, I'd prefer to
introduce a generic one to get the handle, and let the application to
call other vhost APIs.
--yliu
