linux-kernel - Re: [PATCH] Prevent reserving RAM in the region already reserved by BIOS

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Message-ID: <4BF4235D.3080904@zytor.com>
Date:	Wed, 19 May 2010 10:43:57 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Yinghai <yinghai.lu@...cle.com>
CC:	Mathieu Rondonneau <mathieu.rondonneau@...il.com>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] Prevent reserving RAM in the region already reserved
 by BIOS

On 05/19/2010 10:40 AM, Yinghai wrote:
> On 05/18/2010 10:35 PM, Mathieu Rondonneau wrote:
>> Does it make sense to prevent looking for stolen RAM below the ISA section.
>>
>>
>> Signed-off-by: Mathieu Rondonneau <mathieu.rondonneau@...il.com>
>> ---
>>  arch/x86/kernel/e820.c |    2 ++
>>  1 files changed, 2 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
>> index 7bca3c6..322c9c3 100644
>> --- a/arch/x86/kernel/e820.c
>> +++ b/arch/x86/kernel/e820.c
>> @@ -1156,6 +1156,8 @@ void __init e820_reserve_resources_late(void)
>>                         end = MAX_RESOURCE_SIZE;
>>                 if (start >= end)
>>                         continue;
>> +               if (end < ISA_START_ADDRESS)
>> +                       continue;
>>                 printk(KERN_DEBUG "reserve RAM buffer: %016llx - %016llx ",
>>                                start, end);
>>                 reserve_region_with_split(&iomem_resource, start, end,
> 
> do you notice any changes in /proc/iomem?
> 

It should be harmless to reserve memory which is already reserved, so
this patch is at best a no-op.  Furthermore, it introduces another
instance of special address space (ISA_START_ADDRESS in this case) which
is never a good thing.

	-hpa

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