[OpenBIOS] [Qemu-ppc] FreeBSD powerpc issue

Andreas Tobler andreast at fgznet.ch
Fri Aug 31 22:40:53 CEST 2012

On 27.08.12 23:51, Alexander Graf wrote:
> On 27.08.2012, at 13:43, Segher Boessenkool <segher at kernel.crashing.org> wrote:
>>>>> How do I flush the TLB?
>>>> tlbie, and perhaps tlbsync.
>>> The QEMU TLB only caches existing translations, never misses.
>> I'm not sure what you mean here?  No PowerPC hardware that I know of
>> stores a "this address doesn't go anywhere" tag in the TLB, either
>> (I don't think the architecture allows that even).
>> I also don't see what it has to do with the problem.  The scenario
>> what we think is happening: the CPU has translations for the OF code
>> space in its TLB, because it has run it before.  The kernel removes
>> the translations but doesn't do TLBIE on those.  On real hardware,
>> the TLB entries are still used.  What does QEMU do?
> Ah, I see. It depends. QEMU doesn't provide any guarantees that the TLB survives basically. We don't flush it often for book3s, but it can still happen. Maybe try to put a printf into the tlb flush handler function?

Sorry for the delay, was sick for the past days :(

You suggest to add some printf's, am I right to do that in the cputlb.c 
tlb_flush()? If not, where did you mean to do that?

And on a side note, are/were there successful boot results from other 
OS's than linux with qemu and OpenBIOS on powerpc?

I didn't find a successful report.


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