linux-kernel - Re: i686 quirk for AMD Geode

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Message-ID:  <20091108110512.3cfad100@mycelium.queued.net>
Date:	Sun, 8 Nov 2009 11:05:12 -0500
From:	Andres Salomon <dilinger@...labora.co.uk>
To:	linux-kernel@...r.kernel.org
Subject:  Re: i686 quirk for AMD Geode

See comment below.  BTW, how does this affect performance on LXs?
Do you have any hard numbers for common tasks?

On Sat, 7 Nov 2009 12:11:55 +0100
Matteo Croce <technoboy85@...il.com> wrote:
[...]
> 
> --- a/arch/x86/kernel/Makefile	2009-11-06 15:06:52.246223989
> +0100 +++ b/arch/x86/kernel/Makefile	2009-11-06
> 15:07:04.294054613 +0100 @@ -89,7 +89,7 @@
>  obj-$(CONFIG_HPET_TIMER) 	+= hpet.o
> 
>  obj-$(CONFIG_K8_NB)		+= k8.o
> -obj-$(CONFIG_MGEODE_LX)		+= geode_32.o mfgpt_32.o
> +obj-$(CONFIG_MGEODE_LX)		+= geode_32.o mfgpt_32.o
> nopl_emu.o obj-$(CONFIG_DEBUG_RODATA_TEST)	+= test_rodata.o
>  obj-$(CONFIG_DEBUG_NX_TEST)	+= test_nx.o
> 
> --- a/arch/x86/kernel/cpu/amd.c	2009-11-06 15:06:52.254223805
> +0100 +++ b/arch/x86/kernel/cpu/amd.c	2009-11-06
> 15:07:04.294054613 +0100 @@ -138,8 +138,10 @@
>  	}
> 
>  	if (c->x86_model == 10) {
> -		/* AMD Geode LX is model 10 */
> -		/* placeholder for any needed mods */
> +		/* Geode only lacks the NOPL instruction to be i686,
> +		   but we can emulate it in the exception handler
> +		   and promote it to a class 6 cpu */
> +		boot_cpu_data.x86 = 6;
>  		return;
>  	}

If you're going to update this, you also need to make sure that you're
not breaking things that check it.  For example,
arch/x86/include/asm/geode.h has an is_geode_lx check that expects
boot_cpu_data.x86 to be 5.  Please be sure to update all these places
when creating a patch like this.


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