Venki Pallipadi wrote:
On Tue, Jan 15, 2008 at 09:16:50AM -0800, Jeremy Fitzhardinge wrote:
Ingo Molnar wrote:
-#define _PAGE_PRESENT (_AC(1, UL)<<_PAGE_BIT_PRESENT)
-#define _PAGE_RW (_AC(1, UL)<<_PAGE_BIT_RW)
-#define _PAGE_USER (_AC(1, UL)<<_PAGE_BIT_USER)
-#define _PAGE_PWT (_AC(1, UL)<<_PAGE_BIT_PWT)
-#define _PAGE_PCD ((_AC(1, UL)<<_PAGE_BIT_PCD) | _PAGE_PWT)
BTW, I just noticed that _PAGE_PWT has been folded into _PAGE_PCD. This
seems like a really bad idea to me, since it breaks the rule that
_PAGE_X == 1 << _PAGE_BIT_X. I can't think of a specific place where
this would cause problems, but this kind of non-uniformity always ends
up biting someone in the arse.
I think having a specific _PAGE_NOCACHE which combines these bits is a
better approach.
J
How about the patch below. It defines new _PAGE_UC. One concern is drivers
continuing to use _PAGE_PCD and getting wrong attributes. May be we need to
rename _PAGE_PCD to catch those errors as well?
Sure, looks fine. I would have said that _NOCACHE matches current usage
better, but if it makes more sense to have _UC and _WC then that's fine
with me.
I guess renaming _PAGE_BIT_PCD to _PAGE_BIT__PCD and the corresponding
_PAGE__PCD might be reasonable if you think there's a chance of new
misusers appearing (I guess something like out of tree DRI/proprietary
patches are a source of that).
J
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