Re: [gentoo-user] dmesg warning about mtrr: type mismatch and allocation failed

[Bill Longman]

On 08/19/2010 04:37 AM, Walter Dnes wrote:
> On Mon, Aug 16, 2010 at 05:55:04PM -0500, Paul Hartman wrote
>>
>> I had a similar message, it was there because of the fact that i
>> specified the wrong (or failed to specify?) mtrr method in my kernel
>> boot parameters for the framebuffer. I'm using uvesafb and in kernel
>> documentation (/usr/src/linux/Documentation/fb/uvesafb.txt) it
>> explains the values and even gives an example of this error and what
>> to do about it:
>
>   I'm using the Intel driver, which doesn't have those settings.  And
> no, I do not want to drop down to a generic VESA driver with no hardware
> acceleration.  Some more Google searching has turned up a lead.
> Apparently, it's possible to manually set the mtrr's, using cat and echo
> with /proc/mtrr
>
>   According to "lspci -v", my integrated graphics chip has
>
>         Memory at fb800000 (64-bit, non-prefetchable) [size=4M]
>         Memory at d0000000 (64-bit, prefetchable) [size=256M]
>
>   My mtrr setup, however, shows up like so...
>
> waltdnes@i3 ~ $ cat /proc/mtrr
> reg00: base=0x000000000 (    0MB), size= 8192MB, count=1: write-back
> reg01: base=0x200000000 ( 8192MB), size= 1024MB, count=1: write-back
> reg02: base=0x0c0000000 ( 3072MB), size= 1024MB, count=1: uncachable
> reg03: base=0x0b4000000 ( 2880MB), size=   64MB, count=1: uncachable
> reg04: base=0x0b8000000 ( 2944MB), size=  128MB, count=1: uncachable
> reg05: base=0x1fc000000 ( 8128MB), size=   64MB, count=1: uncachable
>
>   I'll read up more on how to set it up manually.  One thing that has my
> curiousity right now... how come there's a gig of ram in write-back mode
> *STARTING* at 8 gigs, and ending at 9 gigs minus 1 byte, when I only
> have 8 gigs of ram in total?

You might want to have a look in your kernel Documentation directory.
There's a file x86/mtrr.txt that gives you some info. And lots in the fb
subdirectory. You can probably find some other info there, too. There's
lots of the dreaded MTRR info in the kernel_parameters.txt file, so you
can setup the MTRRs at boot time.