Hole in kernel virtual address space.

["Raymond B. Jennings III" <raymondj@watson.ibm.com>]

I've asked this question in the past but have yet to get any insight to
it.

Basically there appears to be a hole when HIGHMEM is turned on in the
kernel.

With HIGHMEM turned off:
VMALLOC_END = FIXADDR_START - 2*PAGE_SIZE
VMALLOC_END = (FFFFE000h - 4*PAGE_SIZE) - 2*PAGE_SIZE
(Pretty close to the 4GB boundary)

With HIGHMEM turned on:

VMALLOC_END = PKMAP_BASE - 2*PAGE_SIZE

I realize you need room for the pkmap_count array but the array only
allows for 1024 pages.  If PKMAP_BASE = FE000000h then this fills the
address space upto
FE400000.  What is being used in the remaining section of the address
space?  Thanks.

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