Re: [dpdk-dev] [PATCH v2 4/4] add ABI checks

["Trahe, Fiona" <fiona.trahe@intel.com>]

> -----Original Message-----
> From: Thomas Monjalon <thomas@monjalon.net>
> Sent: Tuesday, February 4, 2020 4:00 PM
> To: Trahe, Fiona <fiona.trahe@intel.com>
> Cc: David Marchand <david.marchand@redhat.com>; nhorman@tuxdriver.com; bluca@debian.org;
> ktraynor@redhat.com; Ray Kinsella <mdr@ashroe.eu>; dev@dpdk.org; Akhil Goyal
> <akhil.goyal@nxp.com>; Yigit, Ferruh <ferruh.yigit@intel.com>; Ananyev, Konstantin
> <konstantin.ananyev@intel.com>; dev@dpdk.org; Anoob Joseph <anoobj@marvell.com>; Kusztal,
> ArkadiuszX <arkadiuszx.kusztal@intel.com>; Richardson, Bruce <bruce.richardson@intel.com>;
> Mcnamara, John <john.mcnamara@intel.com>; dodji@seketeli.net; Andrew Rybchenko
> <arybchenko@solarflare.com>; aconole@redhat.com
> Subject: Re: [dpdk-dev] [PATCH v2 4/4] add ABI checks
> 
> 04/02/2020 16:52, Trahe, Fiona:
> >
> > > We are working on a patch, when it is ready we will send it.
> > > If it's not ready by end of your today, of course, go ahead with (b) and
> > > we will work towards 20.05.
> >
> > We will not be sending a patch today.
> > The patch we're working on will provide two versions of rte_cryptodev_info_get(),
> > both call the same PMD function from the dev_ops info_get fn ptr.
> > The default version operates s as normal, the 19.11 version searches
> > through the list returned by the PMD, looking for sym.aead.algo = ChaChaPoly, it needs to strip it from
> the list.
> > As PMDs just pass a ptr to their capabilities list ( it isn't a linked list, but an array
> > with an end marker  = RTE_CRYPTODEV_END_OF_CAPABILITIES_LIST) if the API
> > layer detects Chacha it must allocate some space and store a local copy of the
> > trimmed list. This must be stored only once per device.
> 
> I don't understand what you have to store.
> Can't you just set the algo to 0 if it is ChaCha?
[Fiona] it returns a pointer to data in the PMD domain, which the API couldn't and shouldn't overwrite, e.g.
static const struct rte_cryptodev_capabilities qat_gen3_sym_capabilities[]

> 
> > This versioning will apply to any PMD which wants to take advantage of the new API between now and
> 20.11.
> >
> > Note, I expect the ABI checker tools will still complain of ABI breakage as the LIST_END value will still
> change.
> 
> Right, you need to update the ignore list for the tool.
> 
> > We are also reviewing all other cryptodev APIs in case there is any other API which needs versioning.
> >
> > Anyone see any problem with this approach?
> 
> The other issue is with all other functions accepting this enum as input.
> We should continue returning an error if getting Chacha as input with
> 19.11 version of these functions.
> But I would tend to consider this small ABI breakage can be ignored
> as it is in the error path.
[Fiona] The QAT PMD tests for and handles this error. I expect other PMDs do too.