linux-kernel - Re: [lkp-robot] [x86/kconfig] 81d3871900: BUG:unable_to_handle

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Date:   Fri, 13 Oct 2017 13:01:59 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Christopher Lameter <cl@...ux.com>,
        kernel test robot <xiaolong.ye@...el.com>,
        Ingo Molnar <mingo@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Jiri Slaby <jslaby@...e.cz>,
        Mike Galbraith <efault@....de>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>, LKP <lkp@...org>,
        linux-mm <linux-mm@...ck.org>, Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Megha Dey <megha.dey@...ux.intel.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>
Subject: Re: [lkp-robot] [x86/kconfig] 81d3871900: BUG:unable_to_handle_kernel

On Fri, Oct 13, 2017 at 12:09 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> On Fri, Oct 13, 2017 at 6:56 AM, Andrey Ryabinin
> <aryabinin@...tuozzo.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.