Re: [PATCH 1/4] x86_64: Switch to SPARSE_VIRTUAL

Christoph Lameter
2007-04-02T15:44:30Z

On Sun, 1 Apr 2007, Andi Kleen wrote:

> And when you reserve virtual space somewhere you should
> update Documentation/x86_64/mm.txt. Also you didn't adjust
> the end of the vmalloc area so in theory vmalloc could run
> into your vmemmap.

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 ...