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From: Andy Lutomirski <luto@kernel.org>
Date: Fri, 13 Oct 2017 13:01:59 -0700
Message-ID: <CALCETrV91zeKc__be4otCp_68HYjwobTEPpTEcu69-1FBQBHww@mail.gmail.com>
Subject: Re: [lkp-robot] [x86/kconfig] 81d3871900: BUG:unable_to_handle_kernel
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To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>, Josh Poimboeuf <jpoimboe@redhat.com>, Christopher Lameter <cl@linux.com>, kernel test robot <xiaolong.ye@intel.com>, Ingo Molnar <mingo@kernel.org>, Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@alien8.de>, Brian Gerst <brgerst@gmail.com>, Denys Vlasenko <dvlasenk@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>, Jiri Slaby <jslaby@suse.cz>, Mike Galbraith <efault@gmx.de>, Peter Zijlstra <peterz@infradead.org>, Thomas Gleixner <tglx@linutronix.de>, LKML <linux-kernel@vger.kernel.org>, LKP <lkp@01.org>, linux-mm <linux-mm@kvack.org>, Pekka Enberg <penberg@kernel.org>, David Rientjes <rientjes@google.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Andrew Morton <akpm@linux-foundation.org>, Megha Dey <megha.dey@linux.intel.com>, Herbert Xu <herbert@gondor.apana.org.au>, "David S. Miller" <davem@davemloft.net>, Linux Crypto Mailing List <linux-crypto@vger.kernel.org>

On Fri, Oct 13, 2017 at 12:09 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Fri, Oct 13, 2017 at 6:56 AM, Andrey Ryabinin
> <aryabinin@virtuozzo.com> wrote:
>>
>> This could be fixed by s/vmovdqa/vmovdqu change like bellow, but maybe the right fix
>> would be to align the data properly?
>
> I suspect anything that has the SHA extensions should also do
> unaligned loads efficiently. The whole "aligned only" model is broken.
> It's just doing two loads from the state pointer, there's likely no
> point in trying to align it.
>
> So your patch looks fine, but maybe somebody could add the required
> alignment to the sha256 context allocation (which I don't know where
> it is).

IIRC if we try the latter, then we'll risk hitting the #*!&@% gcc bug
that mostly prevents 16-byte alignment from working on GCC before 4.8
or so.  That way lies debugging disasters.

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