linux-kernel - Re: MPTable can not be high-memory on Linux

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Date:	Sun, 22 Feb 2009 22:14:56 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Ingo Molnar <mingo@...e.hu>
CC:	"Kevin O'Connor" <kevin@...onnor.net>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Stefan Reinauer <stepan@...esystems.de>,
	linux-kernel@...r.kernel.org, coreboot@...eboot.org,
	Jaswinder Singh Rajput <jaswinder@...radead.org>
Subject: Re: MPTable can not be high-memory on Linux

Ingo Molnar wrote:
> * Kevin O'Connor <kevin@...onnor.net> wrote:
> 
>> On Sun, Feb 22, 2009 at 01:33:35PM -0800, Yinghai Lu wrote:
>> [...]
>>>>>>  BIOS-e820: 0000000000090000 - 0000000000100000 (reserved)
>>>>>>  BIOS-e820: 0000000000100000 - 000000003f7f0000 (usable)
>>>>>>  BIOS-e820: 000000003f7f0000 - 0000000040000000 (reserved)
>> [...]
>>>>>> found SMP MP-table at [c00f9fc0] 000f9fc0
>> [...]
>>> that should work for a long time.
>>>
>>> 0xf9fc0 < 1M is quite < max_low_pfn, so wonder why bootmem could panic.
>> On this machine the mptable "floating" structure is at 
>> 0xf9fc0.  It points to the rest of the table which is in the 
>> 0x3f7f0000 area.
>>
>> Note, that this is on a Coreboot+SeaBIOS machine - so we can 
>> change the bios.  However, the mptable spec does allow for 
>> part of the table to be high memory.
> 
> yes, and i'd prefer if it worked fine even if it's that high.
> 

please check

[PATCH] x86: check physptr with max_low_pfn on 32bit

Impact: fix bug

coreboot aka LinuxBIOS try to put mptable on somewhere much high than
max_low_pfn, it cause panic

so need to check physptr with max_low_pfn * PAGE_SIZE.

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

---
 arch/x86/kernel/mpparse.c |   15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

Index: linux-2.6/arch/x86/kernel/mpparse.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/mpparse.c
+++ linux-2.6/arch/x86/kernel/mpparse.c
@@ -710,13 +710,22 @@ static int __init smp_scan_config(unsign
 				 * of physical memory; so that simply reserving
 				 * PAGE_SIZE from mpf->physptr yields BUG()
 				 * in reserve_bootmem.
+				 * also need to make sure physptr is below than
+				 * max_low_pfn
+				 * we don't need reserve the area above max_low_pfn
 				 */
 				unsigned long end = max_low_pfn * PAGE_SIZE;
-				if (mpf->physptr + size > end)
-					size = end - mpf->physptr;
-#endif
+
+				if (mpf->physptr < end) {
+					if (mpf->physptr + size > end)
+						size = end - mpf->physptr;
+					reserve_bootmem_generic(mpf->physptr, size,
+							BOOTMEM_DEFAULT);
+				}
+#else
 				reserve_bootmem_generic(mpf->physptr, size,
 						BOOTMEM_DEFAULT);
+#endif
 			}
 
 			return 1;
--
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