[Fwd: [Linuxppc-dev] Re: [Linuxppc-cvs64] CVS: linuxppc64_2_4/arch/ppc64/kernel head.S,,]

David Engebretsen engebret at vnet.ibm.com
Fri Jun 28 06:56:45 EST 2002

Anton Blanchard wrote:
> Hi Dave,
> Thanks for the explanation. I actually have a comment in my tree warning
> about SLB castouts during the exception exit path but hadnt got around
> to fixing it :)
> I think there are more problems than just this one, what if the
> exception took an SLB miss and chose to cast out the kernel segment
> mapping the stack? My understanding is that we should be clearing the MSR
> RI bit during exception exit and then replaying the final parts of the
> exception exit code if necessary.

I'm not sure that we have other exposures like this one.  Certainly in the case
we have identified, we should be ok.  The text is bolted in the SLB so the only
exception should be on the stack address segment.  As long as the kernel stack
is aligned to its size, we will only take the one exception & then the stack
should be ok.  At this point, we are hard disabled and all addresses are bolted
in the HPT.


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