On Sun, 2009-04-19 at 18:21 +0200, Thomas Hellström wrote:
> Jerome Glisse wrote:
> > On Sat, 2009-04-18 at 21:06 +0200, Thomas Hellström wrote:
> >   
> >> Jerome Glisse wrote:
> >>     
> >>> Hi Thomas
> >>>
> >>> I am getting massive error on x86_64, things like :
> >>> BUG: Bad page map in process gnome-session  pte:1f1d1d1d01000000
> >>> pmd:321a6067
> >>> keep filling the log until very bad things happen.
> >>> Do you have any idea what might cause that in ttm ?
> >>> My assumption is that ttm vm code is guilty their.
> >>> Note that on x86 exact same code seem to run fine.
> >>> All this with 2.6.29 final.
> >>>
> >>> Cheers,
> >>> Jerome Glisse
> >>>
> >>>   
> >>>       
> >> Hi, Jerome!
> >>
> >> The TTM code may well be guilty here. I haven't tested x86-64 for a 
> >> while, but I can probably give it a try on openChrome next week.
> >>
> >> /Thomas
> >>     
> >
> > Okay so i really narrowed it down to asking for WC memory, so my guess
> > is that either my CPU (AMD Athlon(tm) Dual Core Processor 4450e) have
> > PAT issue either TTM PAT/WC code is wrong somehow. I haven't time yet
> > to go deeper with this but i think it worked on an Intel Core2 CPU
> > with x86-64. Also it seems other people doesn't have the issue with
> > WC on x86-64.
> >
> > PS: Sorry for all the noise, the bug didn't always showed up quickly so
> > i had false feeling. I am yet unsure it's fully fixed but so far all my
> > test case which triggered it seems to work fine.
> >
> > Cheers,
> > Jerome
> >
> >   
> 
> Jerome,
> I think I missed what the fix was?
> 
> Anyway, for PAT-aware kernels the drm git TTM code is always assuming 
> PAT is enabled and working.
> For production kernels, the function
>  
> pgprot_ttm_x86_wc
> 
> should be replaced by an exported version of x86 pgprot_writecombine.
> 
> FWIW x86-64 seems to work fine here on a 2.6.27 kernel Athlon-64 
> single-core on openChrome.
> 
> /Thomas


Fix is to not ask for WC memory, i will look at this after i cleanup
all my hack to track down this.

Cheers,
Jerome


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