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

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Date:	Wed, 22 Sep 2010 14:00:41 -0700
From:	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>
To:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Cc:	Andi Kleen <ak@...ux.intel.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>,
	linux-rdma <linux-rdma@...r.kernel.org>,
	Bernard Metzler <BMT@...ich.ibm.com>,
	David Miller <davem@...emloft.net>,
	Matthew Wilcox <willy@...ux.intel.com>,
	Roland Dreier <rdreier@...co.com>
Subject: Re: [PATCH 2/2] siw: Add support for CRC32C offload instruction
	using libcrypto crc32c-intel

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.

>  
> > > Need CPUID module auto probing. I have an older patch that needs
> > > some fixes.
> 
> > Hmm, I don't see how that fits in here exactly.  Would you mind
> > elaborating a bit..?
> 
> Unless the module is loaded the optimized algorithm will not be
> available for automatic use. Maybe your patch causes it to autoload
> because of the by-name reference? Identifying modules to load by CPUID
> will let userspace auto load the appropriate ones based on CPU...
> 

Correct, this patch is so that autoload of crc32c-intel.ko 'just works'
and we do the fallback to the legacy slicing by 1x crc32c.ko when the
former is not availabe.

But I definately agree with Andi here that we should just add a wrapper
around the crypto_alloc_hash() usage of crc32c-intel and crc32c for
libcrypto consumers..

Thanks for your comments Jason!

--nab


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