From: "H. Peter Anvin" <hpa@zytor.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: davej@codemonkey.org.uk,
Stephan Diestelhorst <langer_mann@web.de>,
linux-kernel@vger.kernel.org, cpufreq@lists.linux.org.uk
Subject: Re: [PATCH 1/1] Speedfreq-SMI call clobbers ECX
Date: Wed, 05 Mar 2008 08:02:16 -0800 [thread overview]
Message-ID: <47CEC408.2070604@zytor.com> (raw)
In-Reply-To: <20080305153520.GB19300@elte.hu>
Ingo Molnar wrote:
> * Stephan Diestelhorst <langer_mann@web.de> wrote:
>
>> @@ -184,7 +184,7 @@ static void speedstep_set_state (unsigne
>> __asm__ __volatile__(
>> "movl $0, %%edi\n"
>> "out %%al, (%%dx)\n"
>> - : "=b" (new_state), "=D" (result)
>> + : "=b" (new_state), "=D" (result), "=c" (ecx_clobber)
>> : "a" (command), "b" (function), "c" (state), "d" (smi_port), "S" (0)
>> );
>
> stupid suggestion: why not do a pusha/popa around those instructions, to
> make sure everything is restored? This isnt a fastpath and being
> conservative about SMI side-effects cannot hurt ...
>
You can't pusha/popa if you expect a result. You can, of course, push
and pop individual registers.
It's also kind of odd to do "movl $0,%%edi" instead of just setting EDI
as an input.
-hpa
WARNING: multiple messages have this Message-ID (diff)
From: "H. Peter Anvin" <hpa@zytor.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Stephan Diestelhorst <langer_mann@web.de>,
davej@codemonkey.org.uk, cpufreq@lists.linux.org.uk,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] Speedfreq-SMI call clobbers ECX
Date: Wed, 05 Mar 2008 08:02:16 -0800 [thread overview]
Message-ID: <47CEC408.2070604@zytor.com> (raw)
In-Reply-To: <20080305153520.GB19300@elte.hu>
Ingo Molnar wrote:
> * Stephan Diestelhorst <langer_mann@web.de> wrote:
>
>> @@ -184,7 +184,7 @@ static void speedstep_set_state (unsigne
>> __asm__ __volatile__(
>> "movl $0, %%edi\n"
>> "out %%al, (%%dx)\n"
>> - : "=b" (new_state), "=D" (result)
>> + : "=b" (new_state), "=D" (result), "=c" (ecx_clobber)
>> : "a" (command), "b" (function), "c" (state), "d" (smi_port), "S" (0)
>> );
>
> stupid suggestion: why not do a pusha/popa around those instructions, to
> make sure everything is restored? This isnt a fastpath and being
> conservative about SMI side-effects cannot hurt ...
>
You can't pusha/popa if you expect a result. You can, of course, push
and pop individual registers.
It's also kind of odd to do "movl $0,%%edi" instead of just setting EDI
as an input.
-hpa
next prev parent reply other threads:[~2008-03-05 16:02 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-03-05 14:59 [PATCH 1/1] Speedfreq-SMI call clobbers ECX Stephan Diestelhorst
2008-03-05 15:35 ` Ingo Molnar
2008-03-05 15:35 ` Ingo Molnar
2008-03-05 16:02 ` H. Peter Anvin [this message]
2008-03-05 16:02 ` H. Peter Anvin
2008-03-06 8:38 ` Stephan Diestelhorst
2008-03-06 8:51 ` Stephan Diestelhorst
2008-03-06 10:56 ` Ingo Molnar
2008-03-06 10:56 ` Ingo Molnar
2008-03-10 15:05 ` Stephan Diestelhorst
2008-03-10 16:46 ` Andi Kleen
2008-03-10 21:26 ` Stephan Diestelhorst
2008-03-10 21:51 ` Andi Kleen
2008-03-10 21:51 ` Andi Kleen
2008-03-10 23:14 ` Stephan Diestelhorst
2008-03-10 23:14 ` Stephan Diestelhorst
2008-03-11 9:39 ` Ingo Molnar
2008-03-12 15:04 ` Stephan Diestelhorst
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