Re: [dpdk-dev] [EXT] Re: [PATCH v2 4/4] eal: select IOVA mode as VA for default case

[Jerin Jacob Kollanukkaran <jerinj@marvell.com>]

> -----Original Message-----
> From: Burakov, Anatoly <anatoly.burakov@intel.com>
> Sent: Tuesday, July 16, 2019 8:03 PM
> To: Jerin Jacob Kollanukkaran <jerinj@marvell.com>; dev@dpdk.org; John
> McNamara <john.mcnamara@intel.com>; Marko Kovacevic
> <marko.kovacevic@intel.com>
> Cc: thomas@monjalon.net; david.marchand@redhat.com
> Subject: [EXT] Re: [dpdk-dev] [PATCH v2 4/4] eal: select IOVA mode as VA for
> default case
> 
> On 16-Jul-19 2:46 PM, jerinj@marvell.com wrote:
> > From: Jerin Jacob <jerinj@marvell.com>
> >
> > When bus layer selected the preferred mode as RTE_IOVA_DC then select
> > the IOVA mode as RTE_IOVA_VA.
> >
> > The RTE_IOVA_VA selected as the default because,
> >
> > 1) All drivers work in RTE_IOVA_VA mode, irrespective of physical
> > address availability.
> >
> > 2) By default, the mempool, first asks for IOVA-contiguous memory
> > using RTE_MEMZONE_IOVA_CONTIG and this is slow in IOVA as PA mode
> and
> > it may affect the application boot time.
> >
> > Signed-off-by: Jerin Jacob <jerinj@marvell.com>
> > ---
> 
> I should celebrate now :D
> 
> >   doc/guides/prog_guide/env_abstraction_layer.rst | 10 ++++++++--
> >   lib/librte_eal/linux/eal/eal.c                  |  6 ++----
> >   2 files changed, 10 insertions(+), 6 deletions(-)
> >
> > diff --git a/doc/guides/prog_guide/env_abstraction_layer.rst
> > b/doc/guides/prog_guide/env_abstraction_layer.rst
> > index 77307e3a6..1b0343eee 100644
> > --- a/doc/guides/prog_guide/env_abstraction_layer.rst
> > +++ b/doc/guides/prog_guide/env_abstraction_layer.rst
> > @@ -445,8 +445,14 @@ kernels.
> >   - if the preferred mode is RTE_IOVA_PA but there is no access to Physical
> >     Addresses, then EAL init will fail early, since later probing of the devices
> >     would fail anyway,
> > -- if the preferred mode is RTE_IOVA_DC then based on the Physical
> > Addresses
> > -  availability, the preferred mode is adjusted to RTE_IOVA_PA or
> RTE_IOVA_VA.
> > +- if the preferred mode is RTE_IOVA_DC then select the IOVA mode as
> RTE_IOVA_VA.
> > +  The RTE_IOVA_VA selected as the default because,
> > +
> > +#. All drivers work in RTE_IOVA_VA mode, irrespective of physical address
> availability.
> 
> Is there anywhere we can document that any new driver must support both
> before being accepted?

Not sure why new drivers need to support both PA and VA. Do you mean VA?
And not sure where to document this as well if need.

> 
> > +
> > +#. By default, the mempool, first asks for IOVA-contiguous memory using
> ``RTE_MEMZONE_IOVA_CONTIG``,
> > +   and this is slow in IOVA as PA mode and it may affect the application
> boot time.
> 
> I would also add a point about usability improvement for use-cases which
> require large amounts of IOVA-contiguous memory.

I will add in next version:
How about the following, Let me know if any change required.

#. It is easy to enable large amount of IOVA-contiguous memory use-cases with IOVA in VA mode.

> 
> Otherwise,
> 
> Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>