> > 1. Find biggest free block within DMA availible range.
> > 2. Move memory from either side out of the way, like up high in the
> > memory space where ISA DMA can't happen.
> kwr@kwr.hnv.com said:
> > "Move" is the stumbling block here. You don't know what memory
> > regions (forgot the structure names already *sigh*) use a given
> > physical address unless you exhaustively check every PTE of every
> > memory region in every process. Plus the buffer cache.
>
> Plus device drivers. Some pci device may have a pointer to that memory
> there. In other words, it might not be in any kernel tables at all.
True, though it doesn't really change things. The right thing to do is
to keep a reverse mapping for the page and be prepared for the possibility
that the reverse mapping might be marked invalid, i.e. whatever was using
that page was either unknown or just non-virtual...
Keith
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