Re: pgprot_writecombine & shub 1.x

Jes Sorensen
2005-01-21T09:01:58Z

>>>>> "Jesse" = Jesse Barnes <jbarnes@engr.sgi.com> writes:

Jesse> On Thursday, January 20, 2005 1:03 am, Jes Sorensen wrote:
>> What about real memory and mapping it uncached? Do we need to play
>> the same trick before allowing it to be mapped uncached? and for IO
>> memory mapped uncached?

Jesse> Real memory that we map uncached or WC should be in it's own
Jesse> granule. Since we don't have an allocator for that yet, it's
Jesse> generally an unsafe thing to do (there are exceptions though,
Jesse> like the mspec driver). And yes, we should probably be
Jesse> consulting the EFI memory map before setting any attributes on
Jesse> a page (i.e. at memory init time and whenever we change the
Jesse> pgprot bits), but since almost all conventional memory can be
Jesse> mapped uncached or cached, and I think all I/O memory can be
Jesse> mapped uncached, I didn't worry about those cases (well, that
Jesse> and I doubt that many EFI memory maps are up to the task--it
Jesse> would be ashame to break a bunch of otherwise working machines
Jesse> by forcing them to move to a more complete EFI memory map).

I am working on an allocator for that very reason, however I plan to
make it more generic so one can stick more than just uncached memory
into it (in it's own seperate pool of course).

Cheers,
Jes