Re: mtrr madness

Re: mtrr madness

[Robert Hancock]

Lukas Hejtmanek wrote:
> Hello,
> 
> it seems that all linux kernels contain a bug with mtrr:
> 
>  cat /proc/mtrr 
> reg00: base=0x00000000 (   0MB), size=198656MB: write-back, count=1
> reg01: base=0x80000000 (2048MB), size=197120MB: write-back, count=1
> reg02: base=0x9fc00000 (2556MB), size=196612MB: uncachable, count=1
> reg03: base=0x100000000 (4096MB), size=200704MB: write-back, count=1
> reg04: base=0x200000000 (8192MB), size=204800MB: write-back, count=1
> 
> (watch the size)
> 
> it is definitely  present in the kernels 2.6.16, 2.6.24, 2.6.25, 2.6.26.
> 
> 198656 is 0x3080000000, the correct value would be 0x80000000, similarly
> 197120 is 0x3020000000, the correct would be 0x20000000. 

Those are set up by the BIOS, so it would be what's at fault. I think we 
may be adding something to fix this up though?

Re: mtrr madness

[Yinghai Lu]

On Mon, Sep 1, 2008 at 10:19 AM, Robert Hancock <hancockr@shaw.ca> wrote:
> Lukas Hejtmanek wrote:
>>
>> Hello,
>>
>> it seems that all linux kernels contain a bug with mtrr:
>>
>>  cat /proc/mtrr reg00: base=0x00000000 (   0MB), size=198656MB:
>> write-back, count=1
>> reg01: base=0x80000000 (2048MB), size=197120MB: write-back, count=1
>> reg02: base=0x9fc00000 (2556MB), size=196612MB: uncachable, count=1
>> reg03: base=0x100000000 (4096MB), size=200704MB: write-back, count=1
>> reg04: base=0x200000000 (8192MB), size=204800MB: write-back, count=1
>>
>> (watch the size)
>>
>> it is definitely  present in the kernels 2.6.16, 2.6.24, 2.6.25, 2.6.26.
>>
>> 198656 is 0x3080000000, the correct value would be 0x80000000, similarly
>> 197120 is 0x3020000000, the correct would be 0x20000000.
>
> Those are set up by the BIOS, so it would be what's at fault. I think we may
> be adding something to fix this up though?

the fix is in mainline already...,
Author: Yinghai Lu <yhlu.kernel@gmail.com>
Date:   Thu Aug 21 20:24:24 2008 -0700

    x86: work around MTRR mask setting

please try 2.6.27-rc5...

YH

mtrr madness

[Lukas Hejtmanek]

Hello,

it seems that all linux kernels contain a bug with mtrr:

 cat /proc/mtrr 
reg00: base=0x00000000 (   0MB), size=198656MB: write-back, count=1
reg01: base=0x80000000 (2048MB), size=197120MB: write-back, count=1
reg02: base=0x9fc00000 (2556MB), size=196612MB: uncachable, count=1
reg03: base=0x100000000 (4096MB), size=200704MB: write-back, count=1
reg04: base=0x200000000 (8192MB), size=204800MB: write-back, count=1

(watch the size)

it is definitely  present in the kernels 2.6.16, 2.6.24, 2.6.25, 2.6.26.

198656 is 0x3080000000, the correct value would be 0x80000000, similarly
197120 is 0x3020000000, the correct would be 0x20000000. 

cpu info:
processor	: 1
vendor_id	: GenuineIntel
cpu family	: 6
model		: 15
model name	: Intel(R) Xeon(R) CPU            5160  @ 3.00GHz
stepping	: 11
cpu MHz		: 2992.510
cache size	: 4096 KB
physical id	: 0
siblings	: 2
core id		: 1
cpu cores	: 2
apicid		: 1
initial apicid	: 1
fpu		: yes
fpu_exception	: yes
cpuid level	: 10
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca
cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx lm
constant_tsc arch_perfmon pebs bts rep_good pni monitor ds_cpl vmx est tm2
ssse3 cx16 xtpr dca lahf_lm
bogomips	: 5987.46
clflush size	: 64
cache_alignment	: 64
address sizes	: 38 bits physical, 48 bits virtual
power management:


-- 
Lukáš Hejtmánek