Re: Current bk on ppc32: kernel text corruption

[Benjamin Herrenschmidt]

On Fri, 2005-02-18 at 18:09 +1100, Benjamin Herrenschmidt wrote:
> Ok, we may not be over with memory corruption bugs yet. ppc64 now seem
> stable running LTP overnight, but my laptop has a page of kernel .text
> replaced with zero's as soon as I launch X (and just X, no need to launc
> the whole desktop environment).
> 
> I suspect remap_pfn_range() but I haven't checked yet.

Ok, I found it. It's a bug that was there forever it seems, where
radeonfb accel ops may corrupt kernel memory (via bus master from the
radeon chip) when switching back from X, due to X remapping some areas
of the card vs. fbcon calling some radeonfb accel ops before radeonfb
has a chance to re-initialize the chip (when switching back from X).

I'm cooking a workaround patch for 2.6.11, will be ready as soon as I
have tested. Proper fix is to make sure fbcon never calls any fbdev
accel op before the chip has been properly restored (by a set_var call),
but that is beyond the scope of 2.6.11 I suppose...

Ben.


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