From: Tim Chen <tim.c.chen@linux.intel.com>
Subject: Re: [PATCH 3.11-rc1] crypto: Fix boot failure
 duetomoduledependency.
Date: Wed, 17 Jul 2013 14:53:21 -0700
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Cc: herbert@gondor.apana.org.au, linux-kernel@vger.kernel.org,
	linux-crypto@vger.kernel.org
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
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On Thu, 2013-07-18 at 05:50 +0900, Tetsuo Handa wrote:
> Tim Chen wrote:
> > > Therefore, I think possible solutions are either
> > > 
> > >   (a) built-in the dependent modules
> > > 
> > >       # grep crc /lib/modules/3.11.0-rc1+/modules.dep
> > >       kernel/drivers/scsi/sd_mod.ko: kernel/lib/crc-t10dif.ko
> > >       kernel/lib/crc-t10dif.ko:
> > 
> > This approach will increase kernel size for those who are not using
> > t10dif so some people may object.  
> > BTW, The PCLMULQDQ version does not need to be build in.
> 
> sd_mod.ko must choose one from versions available as of loading sd_mod.ko.
> Although it is not needed to built-in the PCLMULQDQ version for fixing the boot
> failure, it is needed to built-in the PCLMULQDQ version for getting performance
> improvement when PCLMULQDQ is supported.
> 
> > Your approach is quite complicated.  I think something simpler like the
> > following will work:
> 
> We cannot benefit from PCLMULQDQ. Is it acceptable for you?


The following code in crct10dif-pclmul_glue.c

static const struct x86_cpu_id crct10dif_cpu_id[] = {
        X86_FEATURE_MATCH(X86_FEATURE_PCLMULQDQ),
        {}
};
MODULE_DEVICE_TABLE(x86cpu, crct10dif_cpu_id);

will put the module in the device table and get the module
loaded, as long as the cpu support PCLMULQDQ. So we should be able
to benefit.

Tim