Hi! On Fri, Nov 26, 2021 at 09:34:44AM +0100, Cédric Le Goater wrote: > 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.
Ah :-) So when was it enabled, do you know? > $ git show 7dbe11acd807 > commit 7dbe11acd807 > Author: Jocelyn Mayer <l_ind...@magic.fr> > 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. This is very specifically for 7450, not 7400, fwiw. 7400 is a nice core, while 7450 is ugly and asymmetric and unbalanced as hell. It can be faster though ;-) Segher
