kernel since 5.6 do not boot anymore on Apple PowerBook

[Giuseppe Sacco]

Il giorno gio, 27/08/2020 alle 12.39 +0200, Christophe Leroy ha
scritto:
> Hi,
> 
> Le 27/08/2020 à 10:28, Giuseppe Sacco a écrit :
[...]
> > Sorry, I made a mistake. The real problem is down, on the same
> > function, when it calls low_sleep_handler(). This is where the problem
> > probably is.
> 
> Great, you spotted the problem.
> 
> I see what it is, it is in low_sleep_handler() in 
> arch/powerpc/platforms/powermac/sleep.S
> 
> All critical registers are saved on the stack. At restore, they are 
> restore BEFORE re-enabling MMU (because they are needed for that). But 
> when we have VMAP_STACK, the stack can hardly be accessed without the 
> MMU enabled. tophys() doesn't work for virtual stack addresses.
> 
> Therefore, the low_sleep_handler() has to be reworked for using an area 
> in the linear mem instead of the stack.

I am sorry, but I don't know how to fix it. Should I open a bug for
tracking this problem?

Thank you,
Giuseppe