Re: [PATCH 2/2] siw: Add support for CRC32C offload instruction using libcrypto crc32c-intel

["Nicholas A. Bellinger" <nab@linux-iscsi.org>]

On Wed, 2010-09-22 at 15:18 -0600, Jason Gunthorpe wrote:
> [cc list chopped]
> 
> On Wed, Sep 22, 2010 at 02:00:41PM -0700, Nicholas A. Bellinger wrote:
> > On Wed, 2010-09-22 at 14:59 -0600, Jason Gunthorpe wrote:
> > > On Wed, Sep 22, 2010 at 01:38:21PM -0700, Nicholas A. Bellinger wrote:
> > > 
> > > > Indeed, this would clean up the explict RX/TX CRC32C case quite a
> > > > bit..  Unfortuately I am too busy with other items atm to cook up
> > > > this patch, but I would be happy to test it if someone wants to take
> > > > it.  ;)
> > > 
> > > Do you even need to do anything at all? crc32c is provided by
> > > crc32c-intel at a higher priority already, so it should be used if it
> > > is available..
> > 
> > I believe with the current libcrypto code that consumers are still
> > required to explictly ask for crc32c-intel offload.
> 
> Really? It all looks OK to me.. What does your /proc/crypto say on a
> system with crc32c-intel support?

After a fresh boot /proc/crypto looks like:

name         : stdrng
driver       : krng
module       : kernel
priority     : 200
refcnt       : 1
selftest     : passed
type         : rng
seedsize     : 0

name         : crc32c
driver       : crc32c-generic
module       : kernel
priority     : 100
refcnt       : 2
selftest     : passed
type         : shash
blocksize    : 1
digestsize   : 4

name         : sha1
driver       : sha1-generic
module       : kernel
priority     : 0
refcnt       : 1
selftest     : passed
type         : shash
blocksize    : 64
digestsize   : 20

Once I start up the LIO-Target stack and some iSCSI Initiators login
and request crc32c-intel using crypto_alloc_hash() using a method similar
to what this patch for Softiwarp does, the following appears in at the top
of /proc/crypto:

name         : crc32c
driver       : crc32c-intel
module       : crc32c_intel
priority     : 200
refcnt       : 5
selftest     : passed
type         : shash
blocksize    : 1
digestsize   : 4

So I think the main bit here is the ability to request crc32c-intel.ko first,
and then fall back to crc32c.ko when the former is not available on CONFIG_X86.

Best,

--nab