On Apr 19, 2008, at 7:18 AM, Paul Mackerras wrote:
Kumar Gala writes:
[POWERPC] 85xx: Add support for relocatble kernel (and booting at
non-
zero)
Should be OK to go though probably not in the first batch. I want to
look through it carefully again since it's touching code that is
common to a lot of platforms. The patch description looks reasonable
as to what it explains but the english could use a touch-up here or
there (e.g. "a physical address that is module 256M" doesn't actually
mean anything; "a physical address that is 0 modulo 256M" would be
correct).
Ok. I'll have my grammar police review it and repost.
[POWERPC] Port fixmap from x86 and use for kmap_atomic
Once again I want to go through it carefully and understand how it all
works, and in particular understand things like the way it ensures
that the base address for the kmap region is aligned to a 4M boundary
so all the kmap ptes are in a single page (assuming it does :).
I'm not clear on why this is needed. I can see value in having the
PGD entry in place but the pte PAs would be changing all the time so I
don't see what benefit there is in keeping them in one page.
For normal kmap ptes we cover things in one PGD via:
#define PKMAP_BASE ((FIXADDR_BOOT_START - PAGE_SIZE*(LAST_PKMAP +
1)) & PMD_MASK)
The kmap_atomic ptes do NOT have a similar guarantee as they are
controlled via fixmap. However we do "pre-allocate" the PGD via
calling map_page() on all fixmap addresses.
- k
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