4-entry table that must be located within the first 4GB of RAM. This
requirement is met by defining an UMA zone with a custom back-end
allocator function. This revision makes two changes to this back-end
allocator function: (1) It replaces the use of contigmalloc() with the
use of kmem_alloc_contig(). This eliminates "double accounting", i.e.,
accounting by both the UMA zone and malloc tags. (I made the same
change for the same reason to the zones supporting jumbo frames a week
ago.) (2) It passes through the "wait" parameter, i.e., M_WAITOK,
M_ZERO, etc. to kmem_alloc_contig() rather than ignoring it.
pmap_init() calls uma_zalloc() with both M_WAITOK and M_ZERO. At the
moment, this is harmless only because the default behavior of
contigmalloc()/kmem_alloc_contig() is to wait and because pmap_init()
doesn't really depend on the memory being zeroed.
The back-end allocator function in the Xen pmap is dead code. I am
changing it nonetheless because I don't want to leave any "bad examples"
in the source tree for someone to copy at a later date.
Approved by: re (kib)
0e18ab26d0