Bug#523415: corrupted rendering

[Brice Goglin <Brice.Goglin@ens-lyon.org>]

Frederic Peters wrote:
> Brice Goglin wrote:
>
>   
>>> Downgrading the kernel from 2.6.29 to 2.6.26 fixes the problem for
>>> me.
>>>       
>> Any difference in /proc/mtrr between 2.6.26 and 2.6.29 ?
>>     
>
> I downgraged from 2.6.29 to 2.6.28, and it also fixed the problem.
>
> /proc/mtrr in 2.6.28:
> reg00: base=0x000000000 (    0MB), size= 1024MB, count=1: write-back
> reg01: base=0x03ff00000 ( 1023MB), size=    1MB, count=1: uncachable
>
> /proc/mtrr in 2.6.29:
> reg00: base=0x000000000 (    0MB), size= 1024MB, count=1: write-back
> reg01: base=0x03ff00000 ( 1023MB), size=    1MB, count=1: uncachable
> reg02: base=0x0e8000000 ( 3712MB), size=  128MB, count=2: write-combining
>   

So now, booting 2.6.29 and doing as root
    echo "base=0x0e8000000 size=0x8000000 type=write-combining" > /proc/mtrr
might give you the same MTRR back, and might even fix your problems.

Beware that playing with MTRR may be dangerous, so make sure you don't
have critical things running when trying...

Other people: Don't run the above command, you'll have to adapt it to
your machine first.

Brice