On Sun, 2008-01-20 at 20:30 +0200, Mika Penttilà wrote:You have dropped the requirement to map all of low memory (the boot allocator is used for instance to construct physical mem mapping). Either you should fix your INIT_MAP_BEYOND_END or make a big comment telling us why it isn't necessary anymore to map low mem.
I think you are right. The patch ensures that all the initial page
tables themselves have mappings but won't map the additional pages
needed for mapping the rest of lowmem.
However, I think it is no longer necessary to map a whole new 4G worth
of page table pages because the code in kernel_physical_mapping_init now
extends the initial mappings rather than replacing them (see changes to
native_pagetable_setup_start). So now we only need to map 4G worth of
page tables including the initial page tables. That means we only need
to map a fixed set of extra pages rather than the sliding limit
currently used in the patch.
I'm not convinced by the additional 16MB for CONFIG_DEBUG_PAGEALLOC --
we map enough pages for page tables for 4G of lowmem -- adding space for
an extra 16M seems pointless.