RE: gate page oops

From: Luck, Tony <tony.luck_at_intel.com>
Date: 2005-06-09 03:11:05
>Unless there are any objections, please apply (for 2.6.12, hopefully).

I still don't really understand why there are still any "PERCPU_PAGE_SIZE"
references in this code.

It looks like if we are building with a buggy linker, then we workaround
problems by having two separate pages in our vmlinux image, and we map
them at consecutive virtual pages (of size PAGE_SIZE) at the start of region
5 (GATE_ADDR = 0xa000000000000000).

With a good linker, there is only one page in the vmlinux image, and we map
it twice ... but for some unspecified reason we put the mappings on
PERCPU_PAGE_SIZE boundaries at the start of region 5.  This leaves two holes
(assuming PERCPU_PAGE_SIZE > PAGE_SIZE ... which it is unless PAGE_SIZE=64k).

Why do we need the holes?

Should we also map zero pages in the buggy linker case (since there is a hole
from GATE_ADDR + 2*PAGE_SIZE to FIXADDR_USER_END where there are no mappings).
Or perhaps FIXADDR_USER_END should only be GATE_ADDR + 2*PAGE_SIZE in the
buggy linker case?

-Tony
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Received on Wed Jun 8 13:13:59 2005

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