Le 17/12/13 12:15, Toru Nishimura a écrit :
By design, the TLB is turned off on any exception.
It's a very bad decision.
I don't see why that would cause any serious issue.
I recommend to try to write exception processing handler
for general purpose OS like Linux. Let me ask again
why you want TLB to turn off/on for any occasioni?
Well, if TLB is ON and we take (say) a DTLB miss.
Then if TLB stays ON in the miss handler, the miss handler could
generate an ITLB miss.
Nested exceptions seem like a pain to handler.
Because then you need to save EA quite fast for it not to be overwritten
by another nested exception.
Then you end up pretty much forced to add a locked TLB entry for the
exception vectors.
That would get rid of the previously stated ITLB miss problem.
But then, in the DTLB miss handler, you need to do at least a few loads
and stores ... then you can take a DTLB miss!
So ... what to do? Lock more and more TLB entries?
It seems so convenient to run part of the exception handler with TLB off ...
How would you address the previously stated issues?
Thanks for your help :)
Cheers,
--
Yann Sionneau
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