| Re: [hatari-devel] 68030 MMU work |
[ Thread Index |
Date Index
| More lists.tuxfamily.org/hatari-devel Archives
]
Hi,
> The problem is, that TOS puts the MMU page tables at address 0x700, so
> that's in this special memory area which needs supervisor mode to be
> accesses. Now, when the CPU hits a page fault while being in user mode,
> it either has to temporarily switch to supervisor mode for accessing
> that table or there is some other magic which I did not understand
> yet...
That's an interesting point, indeed. My guess is that when the PMMU
needs information located in the main memory the Alternate Function Code
register SFC signals that this is a supervisor mode access. This way the
PMMU would not be restricted by its own (page table) rules on the one
hand, on the other hand all PMMU rules would still apply to regular
programs, i.e. code not executed internally by the CPU.
Take care
Uwe