From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <3B1D5CDC.966285C1@earthlink.net> Date: Tue, 05 Jun 2001 16:27:40 -0600 From: "Joseph A. Knapka" MIME-Version: 1.0 Subject: Re: temp. mem mappings References: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Timur Tabi Cc: linux-mm@kvack.org List-ID: Timur Tabi wrote: > > ** Reply to message from cohutta on Tue, 5 Jun 2001 > 16:42:52 -0400 > > > I don't really want to play with the page tables if i can help it. > > I didn't use ioremap() because it's real system memory, not IO bus > > memory. > > > > How much normal memory is identity-mapped at boot on x86? > > Is it more than 8 MB? > > Much more. Somewhere between 2 and 4 GB is mapped. Large memory support in > Linux has always confused me, so I can't remember exactly how much is mapped. On x86, it's a little less than 1GB (4G-PAGE_OFFSET-); PAGE_OFFSET is 3GB by default. There is some stuff that happens before that mapping is done, though. All you can absolutely count on when you first enter 32-bit mode is the low 8MB. setup_arch() in arch/i386/kernel/setup.c is the place to look if you want to be sure; paging_init() is called from there. -- Joe -- Joseph A. Knapka "You know how many remote castles there are along the gorges? You can't MOVE for remote castles!" -- Lu Tze re. Uberwald // Linux MM documentation in progress: // http://home.earthlink.net/~jknapka/linux-mm/vmoutline.html * Evolution is an "unproven theory" in the same sense that gravity is. * -- 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/