linux-kernel - Re: i686 quirk for AMD Geode

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Message-ID: <40101cc30910031554w40a0f93ata5decac55cbcba5c@mail.gmail.com>
Date:	Sun, 4 Oct 2009 00:54:03 +0200
From:	Matteo Croce <technoboy85@...il.com>
To:	Gabor Gombas <gombasg@...aki.hu>
Cc:	Arjan van de Ven <arjan@...radead.org>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: i686 quirk for AMD Geode

On Sun, Oct 4, 2009 at 12:32 AM, Gabor Gombas <gombasg@...aki.hu> wrote:
> On Sun, Oct 04, 2009 at 12:04:03AM +0200, Matteo Croce wrote:
>
>> yes cmov and i686 are unrelated but some distros (Debian & co.)
>> compiles libraries for two archs:
>> i486 and i686-cmov so only i686 machines does benefit from cmov.
>> This is why I cared about having an i686 aware userspace but it seems
>> that for a missing instruction I can't do that
>
> You could emulate the missing instruction. As long as it is not really
> used, the performance cost of the emulation should not matter. Of course
> if userspace starts to use long NOPs extensively then it becomes a
> problem.

Emulate? I can replace it with two plain NOPs.
How can I do the "emulation"? trapping SIGILL?
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