Re: [BUG] /proc/mtrr I/O error

["Yinghai Lu" <yhlu.kernel@gmail.com>]

On Tue, Sep 2, 2008 at 8:58 PM, Bob Tracy <rct@gherkin.frus.com> wrote:
> On Tue, Sep 02, 2008 at 04:08:00PM -0700, Yinghai Lu wrote:
>> On Tue, Sep 2, 2008 at 3:46 PM, Andrew Morton <akpm@linux-foundation.org> wrote:
>> > On Fri, 29 Aug 2008 16:38:24 -0500
>> > Bob Tracy <rct@gherkin.frus.com> wrote:
>> >
>> >> With 2.6.27-rc4 and possibly earlier kernels, I see the following:
>> >>
>> >> $ cat /proc/mtrr
>> >> cat: /proc/mtrr: Input/output error
>> >>
>> >> Processor is an AMD K6-III/450.
>> >>
>> >
>> > static int mtrr_open(struct inode *inode, struct file *file)
>> > {
>> >        if (!mtrr_if)
>> >                return -EIO;
>> >
>> >
>> >
>> > Beats me.  Perhaps something broke in mtrr_bp_init().
>> >
>> > It would be useful to know if 2.6.26 worked OK.
>> >
>>
>> two patches needed..
>>
>> http://lkml.org/lkml/2008/9/1/307
>>    [PATCH 4/6] x86: delay early cpu initialization until cpuid is done
>> http://lkml.org/lkml/2008/9/1/308
>>   [PATCH 5/6] x86: move mtrr cpu cap setting early in early_init_xxxx
>
> Krzysztof Helt's quick-and-dirty patch posted a few days ago did the
> trick, but from the descriptions of the above patches, they address the
> problem properly.  Here's what "cat /proc/mtrr" shows with Helt's patch
> and the "nv" driver active for my GeForce2 MX 400 card:
>
> $ cat /proc/mtrr
> reg00: base=0xd0000000 (3328MB), size=  64MB: write-combining, count=1
>
> MTRR sanitization seems to be working properly: the same command shows
> nothing when X isn't running.

did you apply them both
  [PATCH 4/6] x86: delay early cpu initialization until cpuid is done
  [PATCH 5/6] x86: move mtrr cpu cap setting early in early_init_xxxx

YH