linux-kernel - Re: Regression in 2.6.23-pre Was: Problems with 2.6.23-rc6 on AMD Geode LX800

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Date:	Wed, 26 Sep 2007 15:30:07 -0600
From:	"Jordan Crouse" <jordan.crouse@....com>
To:	"H. Peter Anvin" <hpa@...or.com>
cc:	"Joerg Pommnitz" <pommnitz@...oo.com>, cebbert@...hat.com,
	linux-kernel@...r.kernel.org
Subject: Re: Regression in 2.6.23-pre Was: Problems with 2.6.23-rc6 on
 AMD Geode LX800

On 26/09/07 14:20 -0700, H. Peter Anvin wrote:
> Testing this patch now:
> 

> >From 2efa33f81ef56e7700c09a3d8a881c96692149e5 Mon Sep 17 00:00:00 2001
> From: H. Peter Anvin <hpa@...or.com>
> Date: Wed, 26 Sep 2007 14:11:43 -0700
> Subject: [PATCH] [x86 setup] Handle case of improperly terminated E820 chain
> 
> At least one system (a Geode system with a Digital Logic BIOS) has
> been found which suddenly stops reporting the SMAP signature when
> reading the E820 memory chain.  We can't know what, exactly, broke in
> the BIOS, so if we detect this situation, declare the E820 data
> unusable and fall back to E801.
> 
> Also, revert to original behavior of always probing all memory
> methods; that way all the memory information is available to the
> kernel.
> 
> Signed-off-by: H. Peter Anvin <hpa@...or.com>
> Cc: Jordan Crouse <jordan.crouse@....com>
> Cc: Joerg Pommnitz <pommnitz@...oo.com>
> ---
>  arch/i386/boot/memory.c |   30 +++++++++++++++++++++++-------
>  1 files changed, 23 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/i386/boot/memory.c b/arch/i386/boot/memory.c
> index 1a2e62d..bccaa1c 100644
> --- a/arch/i386/boot/memory.c
> +++ b/arch/i386/boot/memory.c
> @@ -20,6 +20,7 @@
>  
>  static int detect_memory_e820(void)
>  {
> +	int count = 0;
>  	u32 next = 0;
>  	u32 size, id;
>  	u8 err;
> @@ -33,14 +34,24 @@ static int detect_memory_e820(void)
>  		      "=m" (*desc)
>  		    : "D" (desc), "a" (0xe820));
>  
> -		if (err || id != SMAP)
> +		/* Some BIOSes stop returning SMAP in the middle of
> +		   the search loop.  We don't know exactly how the BIOS
> +		   screwed up the map at that point, we might have a
> +		   partial map, the full map, or complete garbage, so
> +		   just return failure. */
> +		if (id != SMAP) {
> +			count = 0;
>  			break;
> +		}
>  
> -		boot_params.e820_entries++;
> +		if (err)
> +			break;
> +
> +		count++;
>  		desc++;
> -	} while (next && boot_params.e820_entries < E820MAX);
> +	} while (next && count < E820MAX);
>  
> -	return boot_params.e820_entries;
> +	return boot_params.e820_entries = count;
>  }
>  
>  static int detect_memory_e801(void)
> @@ -89,11 +100,16 @@ static int detect_memory_88(void)
>  
>  int detect_memory(void)
>  {
> +	int err = -1;
> +
>  	if (detect_memory_e820() > 0)
> -		return 0;
> +		err = 0;
>  
>  	if (!detect_memory_e801())
> -		return 0;
> +		err = 0;
> +
> +	if (!detect_memory_88())
> +		err = 0;
>  
> -	return detect_memory_88();
> +	return err;
>  }
> -- 
> 1.5.3.1
> 

Works here with the buggy BIOS.  

Acked-by: Jordan Crouse <jordan.crouse@....com>

Thanks.

-- 
Jordan Crouse
Systems Software Development Engineer 
Advanced Micro Devices, Inc.


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