[dpdk-dev] [EXT] Re: [PATCH v11 2/4] eal: add legacy kni option

[Vamsi Krishna Attunuru]

> -----Original Message-----
> From: Ferruh Yigit <ferruh.yigit at intel.com>
> Sent: Monday, October 21, 2019 5:25 PM
> To: Vamsi Krishna Attunuru <vattunuru at marvell.com>; dev at dpdk.org
> Cc: thomas at monjalon.net; Jerin Jacob Kollanukkaran <jerinj at marvell.com>;
> Kiran Kumar Kokkilagadda <kirankumark at marvell.com>;
> olivier.matz at 6wind.com; anatoly.burakov at intel.com;
> arybchenko at solarflare.com; stephen at networkplumber.org
> Subject: [EXT] Re: [dpdk-dev] [PATCH v11 2/4] eal: add legacy kni option
> 
> External Email
> 
> ----------------------------------------------------------------------
> On 10/21/2019 9:03 AM, vattunuru at marvell.com wrote:
> > From: Vamsi Attunuru <vattunuru at marvell.com>
> >
> > This adds a "--legacy-kni" command-line option. It will be used to run
> > existing KNI applications with DPDK 19.11 and later.
> >
> > Signed-off-by: Vamsi Attunuru <vattunuru at marvell.com>
> > Suggested-by: Ferruh Yigit <ferruh.yigit at intel.com>
> 
> <...>
> 
> > diff --git a/lib/librte_eal/common/eal_options.h
> > b/lib/librte_eal/common/eal_options.h
> > index 9855429..1010ed3 100644
> > --- a/lib/librte_eal/common/eal_options.h
> > +++ b/lib/librte_eal/common/eal_options.h
> > @@ -69,6 +69,8 @@ enum {
> >  	OPT_IOVA_MODE_NUM,
> >  #define OPT_MATCH_ALLOCATIONS  "match-allocations"
> >  	OPT_MATCH_ALLOCATIONS_NUM,
> > +#define OPT_LEGACY_KNI      "legacy-kni"
> > +	OPT_LEGACY_KNI_NUM,
> >  	OPT_LONG_MAX_NUM
> >  };
> 
> Two concerns,
> 
> 1- "legacy-kni" doesn't have enough context
> 
> 2- I prefer to keep existing behavior default, at least for a while, something
> like next LTS etc, meanwhile this patch can be around for a good time and
> can be good to switch.
> 
> Based on above to, what do you think to rename the option to 'kni-iova-va',
> if not set by default it will be "IOVA=PA", when set it will enable "IOVA=VA"
> mode?

Hi Ferruh,

I think the new eal flag(legacy-kni) is quite intuitive. Since release notes will be having the required details about it's purpose and how it enables users to use existing applications on latest dpdk.

Current EAL does set iova as va if bus iommu returns DC, meaning iova=va is the kind of default mode(in most of use cases) and for running kni, we have to explicitly set the flag to run kni in iova=va mode all the time. I think having a flag for legacy usage(PA mode) is more appropriate than having kni-iova-va kind of flag.

Otx2 net pmd that runs on Octeontx2 platforms only supports iova=va mode, we would like to have KNI running by default without any flags passed.