linux-kernel - Re: [tip:x86/mm] x86: make e820_update

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Date:	Sat, 14 Mar 2009 14:32:41 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Ingo Molnar <mingo@...e.hu>
CC:	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/mm] x86: make e820_update_range() handle small range
 update

Ingo Molnar wrote:
> * Yinghai Lu <yinghai@...nel.org> wrote:
> 
>> Ingo Molnar wrote:
>>> * Yinghai Lu <yinghai@...nel.org> wrote:
>>>
>>>> Commit-ID:  78a8b35bc7abf8b8333d6f625e08c0f7cc1c3742
>>>> Gitweb:     http://git.kernel.org/tip/78a8b35bc7abf8b8333d6f625e08c0f7cc1c3742
>>>> Author:     Yinghai Lu <yinghai@...nel.org>
>>>> AuthorDate: Thu, 12 Mar 2009 22:36:01 -0700
>>>> Commit:     Ingo Molnar <mingo@...e.hu>
>>>> CommitDate: Sat, 14 Mar 2009 12:20:07 +0100
>>>>
>>>> x86: make e820_update_range() handle small range update
>>>>
>>>> Impact: enhance e820 code to handle more cases
>>>>
>>>> Try to handle new range which could be covered by one entry.
>>>>
>>>> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
>>>> Cc: jbeulich@...ell.com
>>>> LKML-Reference: <49B9F0C1.10402@...nel.org>
>>>> Signed-off-by: Ingo Molnar <mingo@...e.hu>
>>> -tip testing found a bootup crash + reboot due to this patch.
>>>
>>> config attached. The bootup crashes here:
>>>
>>> [    0.000000] MTRR variable ranges enabled:
>>> [    0.000000]   0 base 0000000000 mask FFC0000000 write-back
>>> [    0.000000]   1 disabled
>>> [    0.000000]   2 disabled
>>> [    0.000000]   3 disabled
>>> [    0.000000]   4 disabled
>>> [    0.000000]   5 disabled
>>> [    0.000000]   6 disabled
>>> [    0.000000]   7 disabled
>>> [    0.000000] x86 PAT enabled: cpu 0, old 0x7040600070406, new 0x7010600070106
>>> [    0.000000]   get_mtrr: cpu0 reg00 base=0000000000 size=0000040000 write-back
>>> [    reboot  ]
>>>
>> what does the e820 map look like?
> 
> [    0.000000] BIOS-provided physical RAM map:
> [    0.000000]  BIOS-e820: 0000000000000000 - 000000000009f800 (usable)
> [    0.000000]  BIOS-e820: 000000000009f800 - 00000000000a0000 (reserved)
> [    0.000000]  BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
> [    0.000000]  BIOS-e820: 0000000000100000 - 000000003fff0000 (usable)
> [    0.000000]  BIOS-e820: 000000003fff0000 - 000000003fff3000 (ACPI NVS)
> [    0.000000]  BIOS-e820: 000000003fff3000 - 0000000040000000 (ACPI data)
> [    0.000000]  BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
> [    0.000000]  BIOS-e820: 00000000fec00000 - 0000000100000000 (reserved)
> 

it seems that patch revealed the bug in setup_bios_corruption_check

please check, and apply follow at first, and apply that patch later.

YH

[PATCH] x86: fix 64k corruption checking

Impact: fix crash

need that exit early if the addr far above 64k

Signed-off-by: Yinghai Lu <yinghai@...nel.org>

---
 arch/x86/kernel/check.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Index: linux-2.6/arch/x86/kernel/check.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/check.c
+++ linux-2.6/arch/x86/kernel/check.c
@@ -86,12 +86,12 @@ void __init setup_bios_corruption_check(
 		if (!(addr + 1))
 			break;
 
+		if (addr >= corruption_check_size)
+			break;
+
 		if ((addr + size) > corruption_check_size)
 			size = corruption_check_size - addr;
 
-		if (size == 0)
-			break;
-
 		e820_update_range(addr, size, E820_RAM, E820_RESERVED);
 		scan_areas[num_scan_areas].addr = addr;
 		scan_areas[num_scan_areas].size = size;
--
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