[PATCH 2/2] crypto: talitos: Add AES-XTS Support

[Martin Hicks]

On Thu, Mar 5, 2015 at 7:16 PM, Kim Phillips <kim.phillips at freescale.com> wrote:
> On Fri, 20 Feb 2015 12:00:10 -0500
> Martin Hicks <mort at bork.org> wrote:
>
>> The newer talitos hardware has support for AES in XTS mode.
>
> Assuming it's the same thing, AES-XCBC gets added with SEC v3.0
> h/w.  Assuming hw_supports() doesn't already support this algorithm

AES-XCBC isn't the same thing as AES-XTS.

> combination (technically via the mode bit), this needs to be
> reflected in the patch so the driver doesn't think SEC 2.x devices
> can do XTS, too.

Right.  I hadn't looked into how exactly hw_supports() works.  It only
indicates which execution units are present (in this case the AES
unit).  I actually think XTS gets introduced in SEC v3.3.2.  I also
have an MPC8379 (sec3.3) and it does not have XTS.

Can you look internally to find out in which hardware it was
introduced?  Is there a SEC 3.3.1 that also has XTS?

I guess I just need a ->features flag to conditionally register the
XTS algorithm for 3.3.x and newer.  Adding anything more complicated
doesn't seem warranted at this time, although that could change if
someone came along and needed to add a whole whack more of the AES
modes that were introduced at various times in the different SEC
revisions.

>
>> +             .desc_hdr_template = DESC_HDR_TYPE_COMMON_NONSNOOP_NO_AFEU |
>> +                                     DESC_HDR_SEL0_AESU |
>> +                                     DESC_HDR_MODE0_AESU_XTS,
>
> ...
>
>>  /* primary execution unit mode (MODE0) and derivatives */
>>  #define      DESC_HDR_MODE0_ENCRYPT          cpu_to_be32(0x00100000)
>>  #define      DESC_HDR_MODE0_AESU_CBC         cpu_to_be32(0x00200000)
>> +#define      DESC_HDR_MODE0_AESU_XTS         cpu_to_be32(0x04200000)
>
> I'd prefer these defines be kept as single bit definitions, and keep
> their names from the manual.  An XTS-specific definition can be
> composed from them either after this, or manually in the
> desc_hdr_template assignment above.

It doesn't look like there are divisible single-bit definitions for
the MODE0 bits. The AES Cipher modes are composed of 5 bits called
CipherMode, Extended CipherMode and Aux2.  Individually they don't
seem to mean anything.  Unless you want something like:

#define AES_MODE(cm, ecm, aux2)   cpu_to_be32(((ecm<<6) | (aux2<<5) |
(cm<<1)) << 20)

#define DESC_HDR_MODE0_AESU_CBC  AES_MODE(1, 0, 0)
#define DESC_HDR_MODE0_AESU_XTS   AES_MODE(1, 1, 0)

Thanks,
mh

-- 
Martin Hicks P.Eng.      |         mort at bork.org
Bork Consulting Inc.     |   +1 (613) 266-2296