On 11/25/21 10:38, Segher Boessenkool wrote:
On Thu, Nov 25, 2021 at 01:45:00AM +0100, BALATON Zoltan wrote:
As for guests, those running on the said PowerMac G4 should have support for these CPUs so maybe you can try some Mac OS X versions (or maybe
OSX uses hardware pagetables.
MorphOS but that is not the best for debugging as there's no source available nor any help from its owners but just to see if it boots it may be sufficient, it should work on real PowerMac G4).
I have no idea what MorphOS uses, but I bet HPT as well. That is because HPT is fastest in general. Software TLB reloads are good in special cases only; the most common is real-time OSes, which can use its lower guaranteed latency for some special address spaces (and can have a simpler address map in general).
The support was added to QEMU knowing that Linux didn't handle soft TLBs. And the commit says that it was kept disabled initially. I guess that was broken these last years.
$ git show 7dbe11acd807 commit 7dbe11acd807 Author: Jocelyn Mayer email@example.com Date: Mon Oct 1 05:16:57 2007 +0000
Handle all MMU models in switches, even if it's just to abort because of lack of supporting code. Implement 74xx software TLB model. Keep 74xx with software TLB disabled, as Linux is not able to handle TLB miss on those processors.