Re: [dpdk-dev] [PATCH] ethdev: limit maximum number of queues

[David Marchand <david.marchand@redhat.com>]

On Wed, Nov 27, 2019 at 3:11 PM Thomas Monjalon <thomas@monjalon.net> wrote:
>
> 27/11/2019 15:07, David Marchand:
> > On Wed, Nov 27, 2019 at 3:06 PM Ferruh Yigit <ferruh.yigit@intel.com> wrote:
> > >
> > > On 11/27/2019 1:42 PM, Thomas Monjalon wrote:
> > > > A buffer overflow happens in testpmd with some drivers
> > > > since the queue arrays are limited to RTE_MAX_QUEUES_PER_PORT.
> > > >
> > > > The advertised capabilities of mlx4, mlx5 and softnic
> > > > for the number of queues were the maximum number: UINT16_MAX.
> > > > They must be limited by the configured RTE_MAX_QUEUES_PER_PORT
> > > > that applications expect to be respected.
> > > >
> > > > The limitation is applied in above drivers having no limitation,
> > > > and at ethdev level (function rte_eth_dev_info_get), in order
> > > > to force the configured limit for all drivers.
> > >
> > > The limit is not device limit, should we reflect it into PMDs?
> > > Why not keep the limit only in the ethdev?
> >
> > +1.
>
> Yes ethdev is enough.
> I thought it would be better to document the limit in the PMDs as well,
> instead of keeping gigantic max.

This gigantic value also documents that the driver has no limitation itself.
The limitation is in the ethdev layer.

Certainly a bit far-fetched but, with the mlx5 driver as a .so, you
would prefer the driver not to announce a limitation from ethdev if
you recompile ethdev.

--
David Marchand