Re: [dpdk-dev] [RFC v2, 1/2] cryptodev: add support to set session private data

["De Lara Guarch, Pablo" <pablo.de.lara.guarch@intel.com>]

Hi Abhinandan,

> -----Original Message-----
> From: Gujjar, Abhinandan S
> Sent: Thursday, January 25, 2018 3:38 PM
> To: De Lara Guarch, Pablo <pablo.de.lara.guarch@intel.com>; Doherty,
> Declan <declan.doherty@intel.com>; akhil.goyal@nxp.com;
> Jerin.JacobKollanukkaran@cavium.com
> Cc: dev@dpdk.org; Vangati, Narender <narender.vangati@intel.com>; Rao,
> Nikhil <nikhil.rao@intel.com>
> Subject: RE: [RFC v2, 1/2] cryptodev: add support to set session private
> data
> 
> Hi Pablo & Declan,
> 
> > -----Original Message-----
> > From: De Lara Guarch, Pablo
> > Sent: Thursday, January 25, 2018 1:17 AM
> > To: Gujjar, Abhinandan S <abhinandan.gujjar@intel.com>; Doherty,
> > Declan <declan.doherty@intel.com>; akhil.goyal@nxp.com;
> > Jerin.JacobKollanukkaran@cavium.com
> > Cc: dev@dpdk.org; Vangati, Narender <narender.vangati@intel.com>;
> Rao,
> > Nikhil <nikhil.rao@intel.com>
> > Subject: RE: [RFC v2, 1/2] cryptodev: add support to set session
> > private data
> >
> >
> >
> > > -----Original Message-----
> > > From: Gujjar, Abhinandan S
> > > Sent: Tuesday, January 23, 2018 8:54 AM
> > > To: Doherty, Declan <declan.doherty@intel.com>;
> akhil.goyal@nxp.com;
> > > De Lara Guarch, Pablo <pablo.de.lara.guarch@intel.com>;
> > > Jerin.JacobKollanukkaran@cavium.com
> > > Cc: dev@dpdk.org; Vangati, Narender <narender.vangati@intel.com>;
> > > Gujjar, Abhinandan S <abhinandan.gujjar@intel.com>; Rao, Nikhil
> > > <nikhil.rao@intel.com>
> > > Subject: [RFC v2, 1/2] cryptodev: add support to set session private
> > > data
> > >
> > > Update rte_crypto_op to indicate private data offset.
> > >
> > > The application may want to store private data along with the
> > > rte_cryptodev that is transparent to the rte_cryptodev layer.
> > > For e.g., If an eventdev based application is submitting a
> > > rte_cryptodev_sym_session operation and wants to indicate event
> > > information required to construct a new event that will be enqueued
> > > to eventdev after completion of the rte_cryptodev_sym_session
> operation.
> > > This patch provides a mechanism for the application to associate
> > > this information with the rte_cryptodev_sym_session session.
> > > The application can set the private data using
> > > rte_cryptodev_sym_session_set_private_data() and retrieve it using
> > > rte_cryptodev_sym_session_get_private_data().
> >
> > Hi Abhinandan,
> >
> > >
> > > Signed-off-by: Abhinandan Gujjar <abhinandan.gujjar@intel.com>
> > > Signed-off-by: Nikhil Rao <nikhil.rao@intel.com>
> > > ---
> > > Notes:
> > >         V2:
> > > 	1. Removed enum rte_crypto_op_private_data_type
> > > 	2. Corrected formatting
> > >
> > >  lib/librte_cryptodev/rte_crypto.h    |  8 ++++++--
> > >  lib/librte_cryptodev/rte_cryptodev.h | 32
> > > ++++++++++++++++++++++++++++++++
> > >  2 files changed, 38 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/lib/librte_cryptodev/rte_crypto.h
> > > b/lib/librte_cryptodev/rte_crypto.h
> > > index 95cf861..14c87c8 100644
> > > --- a/lib/librte_cryptodev/rte_crypto.h
> > > +++ b/lib/librte_cryptodev/rte_crypto.h
> > > @@ -84,8 +84,12 @@ struct rte_crypto_op {
> > >  	 */
> > >  	uint8_t sess_type;
> > >  	/**< operation session type */
> > > -
> > > -	uint8_t reserved[5];
> > > +	uint16_t private_data_offset;
> > > +	/**< Offset to indicate start of private data (if any). The private
> > > +	 * data may be used by the application to store information which
> > > +	 * should remain untouched in the library/driver
> >
> > Is this the offset for the private data after the crypto operation?
> Yes. This is private date is meant for sessionless case.
> > From your title, it looks like it is for the session private data, but
> > then, this shouldn't be here.
> Agree.
> > If it is for the crypto operation, I suggest you to separate it in another
> patch.
> > Also, you should indicate where the offset starts from. For the IV,
> > the offset is counted from the start of the rte_crypto_op, so I think
> > it should be the same, to keep consistency.
> Sure. I will make a separate patch for this changes. Add some more
> information to make it clear.
> >
> > For the session private data, we see two options:
> >
> > 1 - Add a  "valid" private data field in the rte_cryptodev_sym_session
> > structure, so when it is set, it indicates that the session contains
> > private data (a single bit would be enough, 1 to indicate there is, and 0 to
> indicate there is not).
> > This would go into the beginning of the structure, so this would
> > require an ABI deprecation notice.
> > This also assumes that the private data starts just after the session
> > header
> >
> > 2 -  Do not add an extra "valid" private data field in
> > rte_cryptodev_sym_session structure, and add a small header in the
> private data, which contains the "valid"
> > bit.
> > Then, when calling sym_session_get_private_data, this bit should be
> checked.
> > Note that the object that holds the session structure needs to be big
> > enough to hold this value.
> > If the object has only space for the sess_private_data array, then the
> > session has no private data.
> > Therefore, this approach might be less performant, but with no ABI
> > deprecation required.
> I am with option 2 with slight changes as below:
> rte_cryptodev_sym_session_create() will have a flag as below indicating
> private data exits or not.
> {
> - memset(sess, 0, (sizeof(void *) * nb_drivers));
> +memset(sess, 0, (sizeof(void *) * nb_drivers ) +
> +sizeof(private_data_flag));
> }
> and in
> rte_cryptodev_get_header_session_size(void)
> {
>   /*
>    * Header contains pointers to the private data
>    * of all registered drivers
>    */
>   -return (sizeof(void *) * nb_drivers);
>   +return ((sizeof(void *) * nb_drivers) + sizeof(private_data_flag)); } With
> this, a flag indicating private data exists or not will always have valid value.

Sure, this should work. Go ahead and send a v3 with this change, separating the changes
made in the session from the changes made in the crypto operation (so you will have 3 patches in total).

Pablo

> 
> >
> > I would recommend you to send a deprecation notice for option 1, then
> > check the performance of both option, and if needed, make the change
> > in the structure, in 18.05.
> >
> > Regards,
> > Pablo