From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 7 Jan 2008 12:14:45 +0100 From: Nick Piggin Subject: Re: [rfc][patch] mm: use a pte bit to flag normal pages Message-ID: <20080107111445.GB19872@wotan.suse.de> References: <20071221104701.GE28484@wotan.suse.de> <20080107044355.GA11222@wotan.suse.de> <20080107103028.GA9325@flint.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080107103028.GA9325@flint.arm.linux.org.uk> Sender: owner-linux-mm@kvack.org Return-Path: To: Martin Schwidefsky , carsteno@linux.vnet.ibm.com, Heiko Carstens , Jared Hulbert , Linux Memory Management List , linux-arch@vger.kernel.org List-ID: 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org