linux-kernel - Re: [PATCH] powerpc: define empty enable_kernel_vsx() when CONFIG

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Date:	Wed, 9 Sep 2015 07:31:18 -0600
From:	Tim Gardner <tim.gardner@...onical.com>
To:	Michael Ellerman <mpe@...erman.id.au>
Cc:	Paul Mackerras <paulus@...abs.org>, linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Leonidas Da Silva Barbosa <leosilva@...ux.vnet.ibm.com>,
	Herbert Xu <herbert@...dor.apana.org.au>
Subject: Re: [PATCH] powerpc: define empty enable_kernel_vsx() when
 CONFIG_VSX=n

On 09/08/2015 08:13 PM, Michael Ellerman wrote:
> On Tue, 2015-09-08 at 17:19 -0600, Tim Gardner wrote:
>> On 09/08/2015 04:47 PM, Paul Mackerras wrote:
>>> On Tue, Sep 08, 2015 at 12:13:11PM -0600, tim.gardner@...onical.com wrote:
>>>> From: Tim Gardner <tim.gardner@...onical.com>
>>>>
>>>> commit 72cd7b44bc99 ("powerpc: Uncomment and make enable_kernel_vsx()
>>>> routine available") neglected to define an empty inline replacement for
>>>> enable_kernel_vsx() when CONFIG_VSX=n.
>>>
>>> If code that wants to call enable_kernel_vsx() is getting compiled in
>>> when CONFIG_VSX=n, that's a worry.  Is this patch motivated by an
>>> actual compile failure?  If so what was the failure?
>>
>> I was having link failures after backporting 'crypto: nx' patches to a
>> 4.2 based kernel. You may have a point in that the upstream Kconfig will
>> not allow those files to be compiled if CONFIG_VSX=n. I will check in my
>> morning if to see if I can reproduce the same link error in mainline.
>
> I suspect the problem is the "vmx" crypto actually.
>
> $ git grep enable_kernel_vsx drivers/
> drivers/crypto/vmx/aes.c:       enable_kernel_vsx();
> drivers/crypto/vmx/aes.c:               enable_kernel_vsx();
> drivers/crypto/vmx/aes.c:               enable_kernel_vsx();
> drivers/crypto/vmx/aes_cbc.c:   enable_kernel_vsx();
> drivers/crypto/vmx/aes_cbc.c:           enable_kernel_vsx();
> drivers/crypto/vmx/aes_cbc.c:           enable_kernel_vsx();
> drivers/crypto/vmx/aes_ctr.c:   enable_kernel_vsx();
> drivers/crypto/vmx/aes_ctr.c:   enable_kernel_vsx();
> drivers/crypto/vmx/aes_ctr.c:                   enable_kernel_vsx();
> drivers/crypto/vmx/ghash.c:     enable_kernel_vsx();
> drivers/crypto/vmx/ghash.c:                     enable_kernel_vsx();
> drivers/crypto/vmx/ghash.c:                     enable_kernel_vsx();
> drivers/crypto/vmx/ghash.c:                     enable_kernel_vsx();
>
>
> That appears to all be controlled by CONFIG_CRYPTO_DEV_VMX_ENCRYPT, which
> depends on CONFIG_CRYPTO_DEV_VMX, which depends on PPC64.
>
> So that looks like it will break terribly if VSX is turned off.
>
> We do have an automated test build with VSX turned off, but it doesn't have
> CONFIG_CRYPTO_DEV_VMX enabled :/
>
>
> Having said all that, why are you building a ppc64 kernel with VSX turned off?
>
> cheers
>
>

I'm pretty sure my problem is that I'm building a 32bit powerpc with 
CONFIG_CRYPTO_DEV_VMX_ENCRYPT=y, though it is hard to tell for sure with 
the interleaved build output from 4 parallel builds (powerpc-smp 
powerpc64-smp powerpc-e500mc powerpc64-emb). Your proposed patch 
("[PATCH v2] crypto: vmx - VMX crypto should depend on CONFIG_VSX") 
fixes my problems (and makes more sense then my patch), so I suddenly 
don't care as much.

rtg
-- 
Tim Gardner tim.gardner@...onical.com
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