Unmapping pages from the linear addressing without HIGHMEM support

[Benjamin Herrenschmidt]

> That would mean I cannot reuse the code in dma-mapping.c, right? Killing the
> BAT mappings or limiting the memory size covered by the BATs seems to be
> fairly easy, but I guess I have to setup my own page table for the reserved
> DMA memory area and implement my own alloc_pages() function!?

No, just limit the size of the BAT mapping and mark some of the top
pages of the address space reserved... That should be enough.

Ben.