to arrive here referencing the kernel_lev1map without having the
RESERVED ASN -- another CPU may have caused pmap_lev1map_destroy()
to be called, and that routine only invalidates the ASN for the
CPU that called it. So, in the MULTIPROCESSOR case, simply assign
the RESERVED ASN if we reference the kernel_lev1map rather than
asserting that we already have the RESERVED ASN. Thanks to Bill
Sommerfeld for helping me track down the problem.
Also add a new IPI that causes a CPU to re-activate its address
space if the pmap it's using changes level 1 maps (this probably
won't happen very often, but it's correct to have it).
This makes Alpha MP kernels boot multiuser. In fact, this commit
is being made from my dual-CPU AlphaServer 1200 running an MP kernel.
e84fefd1f1