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Date: Wed, 12 May 2010 13:19:43 -0700
From: Yinghai <yinghai.lu@oracle.com>
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To: "H. Peter Anvin" <hpa@zytor.com>
CC: Mike Travis <travis@sgi.com>, Ingo Molnar <mingo@elte.hu>,
       Thomas Gleixner <tglx@linutronix.de>, x86@kernel.org,
       Suresh Siddha <suresh.b.siddha@intel.com>,
       Rusty Russell <rusty@rustcorp.com.au>,
       Jens Axboe <jens.axboe@oracle.com>, Jack Steiner <steiner@sgi.com>,
       LKML <linux-kernel@vger.kernel.org>
Subject: Re: [Patch 1/1] x86 efi: Fill all reserved memmap entries if add_efi_memmap
 specified.
References: <4BEAEF10.9040809@sgi.com> <4BEAF9B6.2040606@zytor.com>
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On 05/12/2010 11:55 AM, H. Peter Anvin wrote:
> On 05/12/2010 11:10 AM, Mike Travis wrote:
>>
>> Currently, the e820_reserve_resources() function does not add entries
>> obtained via the "add_efi_memmap" kernel cmdline option.  This causes
>> /sys/firmware/memmap/... to be incomplete (stops after 128 entries).
>> Utilities that examine these entries then do not get the complete
>> picture of system memory.
>>
>> This patch causes the above function to use the e820 memmap instead
>> of the e820_saved memmap if "add_efi_memmap" cmdline option is
>> specified.
>>
>> Signed-off-by: Mike Travis <travis@sgi.com>
>> Signed-off-by: Jack Steiner <steiner@sgi.com>
> 
> If I'm not mistaken, the very reason for the e820 vs e820_saved map is
> that the latter is supposed to reflect the firmware report, whereas the
> former is subject to be modified by the kernel.  As this is actually a
> reflection of the firmware (although it would be better if you could fix
> the bootloader instead of adding hacks in the kernel...) it really
> should go into e820_saved as well as e820.  Displaying the adjusted e820
> map doesn't seem appropriate under any circumstances.

Yes, you are right.

We should not touch e820_saved and keep /sys/firmware/memmap to be consistent with it.

YH