linux-kernel - Re: [PATCH] x86: Execute WP test after interrupts are enabled

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Message-ID: <84144f020908251258p71d5ad2fx7d31361c243a698e@mail.gmail.com>
Date:	Tue, 25 Aug 2009 22:58:55 +0300
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	mingo@...e.hu, linux-kernel@...r.kernel.org,
	Arnd Hannemann <hannemann@...s.rwth-aachen.de>,
	Brian Gerst <brgerst@...il.com>
Subject: Re: [PATCH] x86: Execute WP test after interrupts are enabled

On Tue, Aug 25, 2009 at 10:53 PM, Jeremy Fitzhardinge<jeremy@...p.org> wrote:
> On 08/25/09 12:38, Pekka Enberg wrote:
>> On Tue, 2009-08-25 at 12:34 -0700, Jeremy Fitzhardinge wrote:
>>
>>> I don't think this is the real fix, and it seems a bit ugly.  I'm OK
>>> with it as a workaround, but I think it will end up getting reverted if
>>> applied.
>>>
>> Yeah, I'm fine with that. It's just that we're really late in the
>> release cycle now so I'd like to keep the fix as simple as possible.
>
> Yeah, that's fine, but I think something like this would be simpler.
> Arnd, could you test it please?
>
> From: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
> Date: Tue, 25 Aug 2009 12:47:17 -0700
> Subject: [PATCH] xen: suppress WP test
>
> Xen always runs on CPUs which properly support WP enforcement in
> privileged mode, so there's no need to test for it.
>
> This also works around a crash reported by Arnd Hannemann, though
> I think its just a band-aid for that case.
>
> Reported-by: Arnd Hannemann <hannemann@...s.rwth-aachen.de>
> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
> Cc: Pekka Enberg <penberg@...helsinki.fi>
>
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index 16d0d70..e5b903b 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1069,6 +1069,7 @@ asmlinkage void __init xen_start_kernel(void)
>        /* set up basic CPUID stuff */
>        cpu_detect(&new_cpu_data);
>        new_cpu_data.hard_math = 1;
> +       new_cpu_data.wp_works_ok = 1;
>        new_cpu_data.x86_capability[0] = cpuid_edx(1);
>  #endif

Yeah, this is even better assuming it works. :-)

Acked-by: Pekka Enberg <penberg@...helsinki.fi>
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