linux-kernel - Re: CPU MTRRs and linux kernel

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Message-ID: <4FD760BC.7030409@canonical.com>
Date:	Tue, 12 Jun 2012 17:31:08 +0200
From:	Stefan Bader <stefan.bader@...onical.com>
To:	Mahmood Naderan <nt_mahmood@...oo.com>
CC:	Borislav Petkov <bp@...en8.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andreas Herrmann <andreas.herrmann3@....com>
Subject: Re: CPU MTRRs and linux kernel

On 12.06.2012 17:15, Mahmood Naderan wrote:
>> And the latest kernel is 2.6.32-41.89 by now...
> 
> Sorry 3.4.2 ???

Not sure what this is intended to mean. From the kernel version you gave in the
initial post I take you are using a Ubuntu 10.04 server installation. And the
latest kernel for that release is 2.6.32-41.89 (which should replace any older
kernel if you do updates).

-Stefan
>  
> 
> // Naderan *Mahmood;
> 
> 
> ----- Original Message -----
> From: Stefan Bader <stefan.bader@...onical.com>
> To: Mahmood Naderan <nt_mahmood@...oo.com>
> Cc: Borislav Petkov <bp@...en8.de>; "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>; Andreas Herrmann <andreas.herrmann3@....com>
> Sent: Tuesday, June 12, 2012 7:43 PM
> Subject: Re: CPU MTRRs and linux kernel
> 
> On 12.06.2012 15:48, Mahmood Naderan wrote:
>> Thanks Borislav,
>> I want to know, should I upgrade to the latest kernel or it is possible to download the source of 2.6.32-24 from repository and modify cleanup.c and then recompile?
>>
> Just update to the latest kernel. 2.6.32-24.39 is way old. The fix Boris
> mentioned was in 2.6.32-27.49. And the latest kernel is 2.6.32-41.89 by now...
> 
> -Stefan
> 
>> ~MN
>>
>> ----- Original Message -----
>> From: Borislav Petkov <bp@...en8.de>
>> To: Mahmood Naderan <nt_mahmood@...oo.com>
>> Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>; Andreas Herrmann <andreas.herrmann3@....com>
>> Sent: Tuesday, June 12, 2012 3:09 PM
>> Subject: Re: CPU MTRRs and linux kernel
>>
>> On Tue, Jun 12, 2012 at 02:37:40AM -0700, Mahmood Naderan wrote:
>>> Hi everybody,
>>> Abour rhis warnning in boot log:
>>>
>>> WARNING: BIOS bug: CPU MTRRs don't cover all of memory, losing 61952MB of RAM
>>>
>>>   
>>> I
>>>    searched a lot however didn't find a clear solution. Does AMD new 
>>> processors (62XX) have problems with new kernels or old kernels??
>>> Mine is:
>>>
>>> Linux n1 2.6.32-24-server #39-Ubuntu SMP Wed Jul 28 06:21:40 UTC 2010 x86_64 GNU/Linux
>>>
>>> Should I upgrade?
>>
>> Yes, fix is below and it got backported to -stable AFAICT but obviously
>> the ubuntus don't have it in the kernel you cite above.
>>
>>
>> commit 3fdbf004c1706480a7c7fac3c9d836fa6df20d7d
>> Author: Andreas Herrmann <andreas.herrmann3@....com>
>> Date:   Thu Sep 30 14:32:35 2010 +0200
>>
>>      x86, mtrr: Assume SYS_CFG[Tom2ForceMemTypeWB] exists on all future AMD CPUs
>>     
>>      Instead of adapting the CPU family check in amd_special_default_mtrr()
>>      for each new CPU family assume that all new AMD CPUs support the
>>      necessary bits in SYS_CFG MSR.
>>     
>>      Tom2Enabled is architectural (defined in APM Vol.2).
>>      Tom2ForceMemTypeWB is defined in all BKDGs starting with K8 NPT.
>>      In pre K8-NPT BKDG this bit is reserved (read as zero).
>>     
>>      W/o this adaption Linux would unnecessarily complain about bad MTRR
>>      settings on every new AMD CPU family, e.g.
>>     
>>      [    0.000000] WARNING: BIOS bug: CPU MTRRs don't cover all of memory, losing 4863MB of RAM.
>>     
>>      Cc: stable@...nel.org # .32.x, .35.x
>>      Signed-off-by: Andreas Herrmann <andreas.herrmann3@....com>
>>      LKML-Reference: <20100930123235.GB20545@...e.amd.com>
>>      Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
>>
>> diff --git a/arch/x86/kernel/cpu/mtrr/cleanup.c b/arch/x86/kernel/cpu/mtrr/cleanup.c
>> index c5f59d071425..ac140c7be396 100644
>> --- a/arch/x86/kernel/cpu/mtrr/cleanup.c
>> +++ b/arch/x86/kernel/cpu/mtrr/cleanup.c
>> @@ -827,7 +827,7 @@ int __init amd_special_default_mtrr(void)
>>
>>          if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
>>                  return 0;
>> -       if (boot_cpu_data.x86 < 0xf || boot_cpu_data.x86 > 0x11)
>> +       if (boot_cpu_data.x86 < 0xf)
>>                  return 0;
>>          /* In case some hypervisor doesn't pass SYSCFG through: */
>>          if (rdmsr_safe(MSR_K8_SYSCFG, &l, &h) < 0)
>>
> --
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