Re: [2.6.25-git18 => 2.6.26-rc1-git1] Xorg crash with xf86MapVidMemerror

[H. Peter Anvin]

Venki Pallipadi wrote:
> On Thu, May 08, 2008 at 01:08:01PM -0700, Rufus & Azrael wrote:
> >    Venki Pallipadi a ecrit :
> >    >
> >    > Use UC_MINUS in reserve_memtype call with -1, when MTRR lookup fails for
> >    any
> >    > reason.
> >    >
> >    > Change the logic in mtrr_type_lookup to just get the type from the start
> >    > address. Using start and end adddress is not right/complete as start and
> >    > end can be covered by different mtrr (where old code will fail) or
> >    > start and end can be in same mtrr, but still have some different
> >    > memory type region in between. Using only start is less restrictive and
> >    > deterministic.
> >    >
> >    > Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@xxxxxxxxx>
> >    >
> >    > ---
> >    >  arch/x86/kernel/cpu/mtrr/generic.c |    7 ++-----
> >    >  arch/x86/mm/pat.c                  |    8 +-------
> >    >  2 files changed, 3 insertions(+), 12 deletions(-)
> >    >
> >
> >    Hi Venki,
> >
> >    Patch applied on 2.6.26-rc1-git5 and all works fine in X server with 
> >    CONFIG_X86_PAT=y.
> >
> >    See dmesg and mtrr files attached.
>
> Thanks for reporting the problem and testing the fix.
> ingo/thomas/hpa: Can you please pick up this patch. Fixes the PAT regression
> reported on this thread.

Hm...

I have *serious* concerns about this; this might paper over this 
particular problem, but it just isn't *correct*.

The fact that the range check is implemented incorrectly is not an 
excuse to just dump it and ignore the problem; it should be fixed instead.

	-hpa
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