Problem with iMacs and kernel entry

Benjamin Herrenschmidt bh40 at
Mon Feb 15 23:41:04 EST 1999

I've just thought about another problem:

Since the new bootx will enter the kernel with MMU disabled, no-one is
allowed to perform any kind of i/o until the MMU is re-enabled. At least
that's my understanding, since cache and speculative pre-fetching are
enabled for the whole address range, including devices.

That means that the iMac "hack" in prom.c that disables the USB
controller will get into trouble, won't it ?

I want to avoid enabling the MMU in the bootstrap to avoid the problem of
TLB misses on 603 (the boostrap has no exception handler) and I don't
like the fact that the kernel entry plays with BATs with MMU enabled.

Any comments ?

           E-Mail: <mailto:bh40 at>
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