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From: Bruce Richardson <bruce.richardson@intel.com>
To: Akhil Goyal <akhil.goyal@nxp.com>
Cc: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>,
	"Gujjar, Abhinandan S" <abhinandan.gujjar@intel.com>,
	"dev@dpdk.org" <dev@dpdk.org>,
	"Doherty, Declan" <declan.doherty@intel.com>,
	"Honnappa.Nagarahalli@arm.com" <Honnappa.Nagarahalli@arm.com>,
	"techboard@dpdk.org" <techboard@dpdk.org>,
	"Vangati, Narender" <narender.vangati@intel.com>,
	"jerinj@marvell.com" <jerinj@marvell.com>
Subject: Re: [dpdk-dev] [dpdk-techboard] [v4 1/3] cryptodev: support enqueue callback functions
Date: Wed, 28 Oct 2020 15:11:30 +0000
Message-ID: <20201028151130.GD1634@bricha3-MOBL.ger.corp.intel.com> (raw)
In-Reply-To: <VI1PR04MB316857318EA0B2299D055488E6170@VI1PR04MB3168.eurprd04.prod.outlook.com>

On Wed, Oct 28, 2020 at 02:28:43PM +0000, Akhil Goyal wrote:
> 
> Hi Konstantin,
> 
> > > > Hi Tech board members,
> > > >
> > > > I have a doubt about the ABI breakage in below addition of field.
> > > > Could you please comment.
> > > >
> > > > >  /** The data structure associated with each crypto device. */  struct
> > > > > rte_cryptodev {
> > > > >  	dequeue_pkt_burst_t dequeue_burst;
> > > > > @@ -867,6 +922,10 @@ struct rte_cryptodev {
> > > > >  	__extension__
> > > > >  	uint8_t attached : 1;
> > > > >  	/**< Flag indicating the device is attached */
> > > > > +
> > > > > +	struct rte_cryptodev_enq_cb_rcu *enq_cbs;
> > > > > +	/**< User application callback for pre enqueue processing */
> > > > > +
> > > > >  } __rte_cache_aligned;
> > > >
> > > > Here rte_cryptodevs is defined in stable API list in map file which is a pointer
> > > > To all rte_cryptodev and the above change is changing the size of the
> > structure.
> > 
> > While this patch adds new fields into rte_cryptodev structure,
> > it doesn't change the size of it.
> > struct rte_cryptodev is cache line aligned, so it's current size:
> > 128B for 64-bit systems, and 64B(/128B) for 32-bit systems.
> > So for 64-bit we have 47B implicitly reserved, and for 32-bit we have 19B
> > reserved.
> > That's enough to add two pointers without changing size of this struct.
> > 
> 
> The structure is cache aligned, and if the cache line size in 32Byte and the compilation
> is done on 64bit machine, then we will be left with 15Bytes which is not sufficient for 2
> pointers.
> Do we have such systems? Am I missing something?
> 

I don't think we support any such systems, so unless someone can point out
a specific case where we need to support 32-byte CLs, I'd tend towards
ignoring this as a non-issue.

> The reason I brought this into techboard is to have a consensus on such change
> As rte_cryptodev is a very popular and stable structure. Any changes to it may
> Have impacts which one person cannot judge all use cases.
>

Haven't been tracking this discussion much, but from what I read here, this
doesn't look like an ABI break and should be ok.

Regards,
/Bruce

  parent reply	other threads:[~2020-10-28 15:12 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-25  9:44 [dpdk-dev] [v4 0/3] support enqueue callbacks on cryptodev Abhinandan Gujjar
2020-10-25  9:44 ` [dpdk-dev] [v4 1/3] cryptodev: support enqueue callback functions Abhinandan Gujjar
2020-10-27 12:47   ` Ananyev, Konstantin
2020-10-27 17:16     ` Gujjar, Abhinandan S
2020-10-27 17:20       ` Ananyev, Konstantin
2020-10-27 17:22         ` Gujjar, Abhinandan S
2020-10-27 18:19   ` Akhil Goyal
2020-10-27 19:16     ` Gujjar, Abhinandan S
2020-10-27 19:26       ` Akhil Goyal
2020-10-27 19:41         ` Gujjar, Abhinandan S
2020-10-27 18:28   ` Akhil Goyal
2020-10-28  8:20     ` Gujjar, Abhinandan S
2020-10-28 12:55       ` Ananyev, Konstantin
2020-10-28 14:28         ` Akhil Goyal
2020-10-28 14:52           ` Ananyev, Konstantin
2020-10-28 15:11           ` Bruce Richardson [this message]
2020-10-28 15:22             ` [dpdk-dev] [dpdk-techboard] " Honnappa Nagarahalli
2020-10-29 13:52               ` Gujjar, Abhinandan S
2020-10-29 14:00                 ` Akhil Goyal
2020-10-30  4:24                   ` Gujjar, Abhinandan S
2020-10-30 17:18                     ` Gujjar, Abhinandan S
2020-10-29 14:26               ` Kinsella, Ray
2020-10-25  9:44 ` [dpdk-dev] [v4 2/3] test: add testcase for crypto enqueue callback Abhinandan Gujjar
2020-10-25  9:44 ` [dpdk-dev] [v4 3/3] doc: add enqueue callback APIs Abhinandan Gujjar
2020-10-26 19:08   ` Akhil Goyal
2020-10-27  3:52     ` Gujjar, Abhinandan S
2020-10-27 12:51   ` Ananyev, Konstantin
2020-10-27 17:17     ` Gujjar, Abhinandan S

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