linux-kernel - Re: [PATCH 0/5] i387: stable kernel backport

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Message-ID: <20120223225934.GA7362@kroah.com>
Date:	Thu, 23 Feb 2012 14:59:34 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Willy Tarreau <w@....eu>, "H. Peter Anvin" <hpa@...or.com>,
	stable@...r.kernel.org, Raphael Prevost <raphael@...o.asia>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/5] i387: stable kernel backport

On Thu, Feb 23, 2012 at 02:38:42PM -0800, Linus Torvalds wrote:
> On Thu, Feb 23, 2012 at 2:27 PM, Willy Tarreau <w@....eu> wrote:
> >
> > OK so indeed I will only be able to check that it boots :-/
> 
> Well, we could do some trivial test-harness that just forces the issue
> with regular timer interrupts (and even without AES-NI). I think Peter
> talked about that when we were trying to hunt it down - but I think he
> was then able to reproduce the problem without anything special and we
> dropped it.
> 
> Essentially, just doing something like
> 
>     if (irq_fpu_usable()) {
>         kernel_fpu_begin();
>         kernel_fpu_end();
>     }
> 
> in do_irq() and do_softirq() would stress-test things even without
> wireless, and even without AES-NI.
> 
> You'd still need an x86-32 machine to test on, because x86-64 was
> immune to this issue.
> 
> But yeah, the impact of this seems to be small enough that for older
> kernels (which are likely used on older systems for maintenance
> anyway) disabling AES-NI on x86-32 really might be the way to go.

I think that's already the case, 2.6.32 has the following depends for
CRYPTO_AES_NI_INTEL:
	depends on (X86 || UML_X86) && 64BIT
It was this way until commit 0d258efb (crypto: aesni-intel - Ported
implementation to x86-32) which showed up in 2.6.38.

So we should be safe for 2.6.32 no changes needed, right?

greg k-h
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