From owner-cvs-src@FreeBSD.ORG Mon Mar 31 00:53:01 2003 Return-Path: Delivered-To: cvs-src@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 9DFB737B404 for ; Mon, 31 Mar 2003 00:53:01 -0800 (PST) Received: from relay.pair.com (relay.pair.com [209.68.1.20]) by mx1.FreeBSD.org (Postfix) with SMTP id C140743F75 for ; Mon, 31 Mar 2003 00:52:59 -0800 (PST) (envelope-from silby@silby.com) Received: (qmail 9047 invoked from network); 31 Mar 2003 08:52:58 -0000 Received: from niwun.pair.com (HELO localhost) (209.68.2.70) by relay.pair.com with SMTP; 31 Mar 2003 08:52:58 -0000 X-pair-Authenticated: 209.68.2.70 Date: Mon, 31 Mar 2003 02:49:30 -0600 (CST) From: Mike Silbersack To: Jake Burkholder In-Reply-To: <20030331052928.GC32298@locore.ca> Message-ID: <20030330235551.L8771@odysseus.silby.com> References: <200303300524.h2U5Ora7061852@repoman.freebsd.org> <20030330201113.GA32298@locore.ca><20030330232030.GB32298@locore.ca> <20030331052928.GC32298@locore.ca> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII cc: cvs-src@FreeBSD.org cc: src-committers@FreeBSD.org cc: cvs-all@FreeBSD.org Subject: Re: HEADS UP Re: cvs commit: src/sys/conf options.i386 src/sys/i386/i386 bios.c locore.s machdep.c mpboot.s pmap.c vm86bios.s vm_machdep.c src/sys/i386/include _types.h bus_at386.h param.h pmap. X-BeenThere: cvs-src@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: CVS commit messages for the src tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 31 Mar 2003 08:53:03 -0000 On Mon, 31 Mar 2003, Jake Burkholder wrote: > PAE makes the page table entries bigger so they can hold 64 bit physical > addresses, but it does not give you more of them, pointers are still 32bit. > On x86 the kernel is mapped into each process' address space, which is why > it takes a chunk of it, and this is how copyin and copyout work, you can > just access the current process' address space directly. All copyin and > copyout do on x86 is handle page faults due to unmapped user memory, which > should not normally happen in kernel mode. If they were separate this would > be much more complicated, and entering the kernel would require switching > address space, instead of just increasing the priviledge level. > > Jake Doh, that makes perfect sense, I didn't think it through before asking. Changing it around to have seperate address spaces sounds like more work than PAE, now that I think more about it. I'll just wait for true 64 bit machines before asking for a large KVA. :) Thanks for the explanation, Mike "Silby" Silbersack