linux-kernel - Re: [PATCH] x86_64: early memtest to find bad ram

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Message-ID: <20080321120313.GD25225@elte.hu>
Date:	Fri, 21 Mar 2008 13:03:13 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	yhlu.kernel@...il.com
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	kernel list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86_64: early memtest to find bad ram

* Yinghai Lu <yhlu.kernel.send@...il.com> wrote:

> do simple memtest after init_memory_mapping
> 
> use find_e820_area_size to find all ram range that is not reserved.
> 
> and do some simple bits test to find some bad ram.
> 
> if find some bad ram, use reserve_early to exclude that range.

very nice patch! I always thought that this was the proper way to do 
memtest - and we could in fact also do something like this after SMP 
bringup, and hit the memory bus via multiple CPUs. [that will need a 
different enumeration though than e820 maps]

one structural observation: please make this unified functionality, so 
that 32-bit kernels can make use of it too.

a small style nit from scripts/checkpatch.pl:

> +//		printk(KERN_DEBUG "find_e820_area_size : e820 %d [%llx, %lx]\n", i, ei->addr, ei_last);

remove such lines or make them pr_debug(). (checkpatch also found more 
such cases)

also, please add a CONFIG_BOOTPARAM_MEMTEST=y option so that 
distributions can enable this by default in their debug kernels.

i've applied your current version to get some testing, please send delta 
patches against x86/latest.

	Ingo
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