linux-kernel - Re: [Patch 1/1] x86 efi: Fill all reserved memmap entries if add_efi

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Date:	Wed, 12 May 2010 13:19:43 -0700
From:	Yinghai <yinghai.lu@...cle.com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Mike Travis <travis@....com>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Jens Axboe <jens.axboe@...cle.com>,
	Jack Steiner <steiner@....com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [Patch 1/1] x86 efi: Fill all reserved memmap entries if add_efi_memmap
 specified.

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@....com>
>> Signed-off-by: Jack Steiner <steiner@....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
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