Re: Bug: Discontigmem virt_to_page() [Alpha,ARM,Mips64?]

Martin J. Bligh
2002-05-02T18:34:41Z

> You don't need any additional common code abstraction to make virtual
> address 3G+256G to point to physical address 1G as in my example above,
> after that you're free to put the physical ram between 1G and 1G+256M
> into the zone normal of node 1 and the stuff should keep working but
> with zone-normal spread in more than one node. You just have full
> control on virt_to_page, pci_map_single, __va. Actually it may be as
> well cleaner to just let the arch define page_address() when
> discontigmem is enabled (instead of hacking on top of __va), that's a
> few liner. (the only true limit you have is on the phys ram above 4G,
> that cannot definitely go into zone-normal regardless if it belongs to a
> direct mapping or not because of pci32 API)

The thing that's special about ZONE_NORMAL is that it's permanently
mapped into kernel virtual address space, so you *cannot* put memory
in other nodes into ZONE_NORMAL without changing the mapping
between physical to virtual memory to a non 1-1 mapping.

No, you don't need to call changing that mapping "CONFIG_NONLINEAR",
but that's basically what the bulk of Dan's patch does, so I think we should
steal it with impunity ;-)

M.