From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Nicholas A. Bellinger" <nab@linux-iscsi.org>
Subject: Re: [PATCH 2/2] siw: Add support for CRC32C offload instruction
	using libcrypto crc32c-intel
Date: Wed, 22 Sep 2010 14:38:31 -0700
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	 <1285187901.1849.85.camel@haakon2.linux-iscsi.org>
	 <20100922205943.GI11157@obsidianresearch.com>
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Cc: linux-kernel <linux-kernel@vger.kernel.org>,
	netdev <netdev@vger.kernel.org>,
	linux-rdma <linux-rdma@vger.kernel.org>,
	Bernard Metzler <BMT@zurich.ibm.com>
To: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
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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