Hi everyone,
> This RFC for proposes several changes inside rte_cryptodev_sym_session.
> Note that this is just RFC not a complete patch, so for now
> I modified only the librte_cryptodev itself,
> some cryptodev PMD, test-crypto-perf and ipsec-secgw example.
> Proposed changes means ABI/API breakage inside cryptodev,
> so looking for feedback from crypto-dev lib and crypto-PMD maintainiers.
> Below are details and reasoning for proposed changes.
>
> 1.rte_cryptodev_sym_session_init()/ rte_cryptodev_sym_session_clear()
> operate based on cytpodev device id, though inside
> rte_cryptodev_sym_session device specific data is addressed
> by driver id (not device id).
> That creates a problem with current implementation when we have
> two or more devices with the same driver used by the same session.
> Consider the following example:
>
> struct rte_cryptodev_sym_session *sess;
> rte_cryptodev_sym_session_init(dev_id=X, sess, ...);
> rte_cryptodev_sym_session_init(dev_id=Y, sess, ...);
> rte_cryptodev_sym_session_clear(dev_id=X, sess);
>
> After that point if X and Y uses the same driver,
> then sess can't be used by device Y any more.
> The reason for that - driver specific (not device specific)
> data per session, plus there is no information
> how many device instances use that data.
> Probably the simplest way to deal with that issue -
> add a reference counter per each driver data.
>
> 2.rte_cryptodev_sym_session_set_user_data() and
> rte_cryptodev_sym_session_get_user_data() -
> with current implementation there is no defined way for the user to
> determine what is the max allowed size of the private data.
> Even within rte_cryptodev_sym_session_set_user_data() we just blindly
> copying user provided data without checking memory boundaries violation.
> To overcome that issue I added 'uint16_t priv_size' into
> rte_cryptodev_sym_session structure.
>
> 3.rte_cryptodev_sym_session contains an array of variable size for
> driver specific data.
> Though number of elements in that array is determined by static
> variable nb_drivers, that could be modified by
> rte_cryptodev_allocate_driver().
> That construction seems to work ok so far, as right now users register
> all their PMDs at startup, though it doesn't mean that it would always
> remain like that.
> To make it less error prone I added 'uint16_t nb_drivers' into the
> rte_cryptodev_sym_session structure.
> At least that allows related functions to check that provided
> driver id wouldn't overrun variable array boundaries,
> again it allows to determine size of already allocated session
> without accessing global variable.
>
> 4.#2 and #3 above implies that now each struct rte_cryptodev_sym_session
> would have sort of readonly type data (init once at allocation time,
> keep unmodified through session life-time).
> That requires more changes in current cryptodev implementation:
> Right now inside cryptodev framework both rte_cryptodev_sym_session
> and driver specific session data are two completely different sctrucures
> (e.g. struct struct null_crypto_session and struct null_crypto_session).
> Though current cryptodev implementation implicitly assumes that driver
> will allocate both of them from within the same mempool.
> Plus this is done in a manner that they override each other fields
> (reuse the same space - sort of implicit C union).
> That's probably not the best programming practice,
> plus make impossible to have readonly fields inside both of them.
> So to overcome that situation I changed an API a bit, to allow
> to use two different mempools for these two distinct data structures.
>
> 5. Add 'uint64_t userdata' inside struct rte_cryptodev_sym_session.
> I suppose that self-explanatory, and might be used in a lot of places
> (would be quite useful for ipsec library we develop).
>
> So the new proposed layout for rte_cryptodev_sym_session:
> struct rte_cryptodev_sym_session {
> uint64_t userdata;
> /**< Can be used for external metadata */
> uint16_t nb_drivers;
> /**< number of elements in sess_data array */
> uint16_t priv_size;
> /**< session private data will be placed after sess_data */
> __extension__ struct {
> void *data;
> uint16_t refcnt;
> } sess_data[0];
> /**< Driver specific session material, variable size */
> };
>
>
> Signed-off-by: Konstantin Ananyev <konstantin.anan...@intel.com>
> ---
Ok, didn't hear any objections, so far,
so I suppose everyone are ok in general with proposed changes.
Will go ahead with deprecation notice for 18.11 then.
Konstantin
