On Mon, Jan 07, 2008 at 10:30:29AM +0000, Russell King wrote: > On Mon, Jan 07, 2008 at 05:43:55AM +0100, Nick Piggin wrote: > > We initially wanted to do the whole vm_normal_page thing this way, with > > another pte bit, but we thought there were one or two archs with no spare > > bits. BTW. I also need this bit in order to implement my lockless > > get_user_pages, so I do hope to get it in. I'd like to know what > > architectures cannot spare a software bit in their pte_present ptes... > > ARM is going to have to use the three remaining bits we have in the PTE > to store the memory type to resolve bugs on later platforms. Once they're > used, ARM will no longer have any room for any further PTE expansion. OK, it is good to have a negative confirmed. So I think we should definitely get the non-pte-bit based mapping schemes working and tested on all platforms before using a pte bit mapping... FWIW, it might be possible for platforms to implement lockless get_user_pages in other ways too. But that's getting ahead of myself. Thanks. - To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
