Ok. will add to the doc in the next release.
No need to adjust the end of the vmalloc area because
the vmemmap starts at the end of it:
include/asm-x86_64/pgtable.h:
#define VMALLOC_START 0xffffc20000000000UL
#define VMALLOC_END 0xffffe1ffffffffffUL
Index: linux-2.6.21-rc5-mm2/include/asm-x86_64/page.h
#define vmemmap ((struct page *)0xffffe20000000000UL)
According to Documentation/x86_64/mm.txt this is an unused hole:
ffffc20000000000 - ffffe1ffffffffff (=45 bits) vmalloc/ioremap space
... unused hole ...
ffffffff80000000 - ffffffff82800000 (=40 MB) kernel text mapping, from phys 0
... unused hole ...
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