linux-kernel - Re: [PATCH 3.11-rc1] crypto: Fix boot failure due to module dependency.

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Message-ID: <3364013.pHWIsx89Eq@vostro.rjw.lan>
Date:	Fri, 19 Jul 2013 15:03:36 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Tim Chen <tim.c.chen@...ux.intel.com>
Cc:	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	herbert@...dor.apana.org.au, linux-kernel@...r.kernel.org,
	linux-crypto@...r.kernel.org, ak <ak@...ux.intel.com>
Subject: Re: [PATCH 3.11-rc1] crypto: Fix boot failure due to module dependency.

On Thursday, July 18, 2013 04:08:14 PM Tim Chen wrote:
> On Fri, 2013-07-19 at 00:17 +0200, Rafael J. Wysocki wrote:
> > On 7/18/2013 11:00 PM, Tim Chen wrote:
> > > On Thu, 2013-07-18 at 12:47 +0900, Tetsuo Handa wrote:
> > >> Tim Chen wrote:
> > >>>>> 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.
> > >> Excuse me, how can crct10dif-pclmul.ko get loaded automatically?
> > >> Did you test CONFIG_CRYPTO_CRCT10DIF_PCLMUL=m with below debug message?
> > > The code:
> > >
> > > static const struct x86_cpu_id crct10dif_cpu_id[] = {
> > >           X86_FEATURE_MATCH(X86_FEATURE_PCLMULQDQ),
> > >           {}
> > > };
> > > MODULE_DEVICE_TABLE(x86cpu, crct10dif_cpu_id);
> > >
> > > causes the following line to be added to modules.alias file:
> > >
> > > alias x86cpu:vendor:*:family:*:model:*:feature:*0081* crct10dif_pclmul
> > >
> > > This should cause udev to load the crct10dif_pclml module when cpu
> > > support the PCLMULQDQ (feature code 0081).  I did my testing during
> > > development on 3.10 and the module was indeed loaded.
> > >
> > > However, I found that the following commit under 3.11-rc1 broke
> > > the mechanism after some bisection.
> > >
> > > commit ac212b6980d8d5eda705864fc5a8ecddc6d6eacc
> > > Author: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > Date:   Fri May 3 00:26:22 2013 +0200
> > >
> > >      ACPI / processor: Use common hotplug infrastructure
> > >      
> > >      Split the ACPI processor driver into two parts, one that is
> > >      non-modular, resides in the ACPI core and handles the enumeration
> > >      and hotplug of processors and one that implements the rest of the
> > >      existing processor driver functionality.
> > >      
> > > Rafael, can you check and see if this can be fixed so those optimized
> > > crypto modules for Intel cpu that support them can be loaded?
> > 
> > I think this is an ordering issue between udev startup and the time when 
> > devices are registered.
> 
> Something that can be fixed?

I'm sure it can be fixes, but I'm not sure whether it's a udev bug or real
breakage in the kernel yet.  I need to figure out that part.

> > I wonder what happens if you put those modules into the initramfs image?
> 
> Under initramfs image's /lib/modules/3.11.0-rc1/kernel/arch/x86/crypto
> directory?  Any files in /lib/modules/3.11.0-rc1/modules.* need to be
> modified?

No, you shouldn't need to modify any files, just please try to make your
mkinitrd (or whatever else you use) put the modules you'd like to be
autoloaded into the image.

That's only something I'd like to know at this point, though, not a
"workaround" or something like that.

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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