Most of the effect of setting MSR[SF] is that the CPU will stop ignoring
the high 32 bits of registers containing addresses in load/store
instructions. As such, the kernel was setting it only when it began to
need access to high memory. MSR[SF] also affects the operation of some
conditional instructions, however, and so setting it at late times could
subtly break code at very early times. This fixes use of the FDT mode in
loader, and FDT boot more generally, on 64-bit PowerPC systems.
Hardware provided by: IBM LTC
Approved by: re (kib)
Much of the code was common to begin with. There is one nit, which is likely
not an issue at all. With the old code, the AIM machdep would __syncicache()
the entire kernel core at setup. However, in the unified setup, that seems to
hang on the MPC7455, perhaps because it's running later than before. Removing
this allows it to boot just fine. Examining the code, the FreeBSD loader
already does syncicache of the full kernel, and each module loaded, so this
doesn't appear to be an actual problem.
Initial code by Nathan Whitehorn.
