From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailserv2.iuinc.com (qmailr@mailserv2.iuinc.com [206.245.164.55]) by puffin.external.hp.com (8.8.7/8.8.7) with SMTP id OAA09540 for ; Tue, 16 Nov 1999 14:41:39 -0700 Received: from xsvr4.cup.hp.com (xsvr4.cup.hp.com [15.0.68.169]) by atlrel1.hp.com (Postfix) with ESMTP id 1861827D4 for ; Tue, 16 Nov 1999 16:43:13 -0500 (EST) Received: from hp.com (localhost [127.0.0.1]) by xsvr4.cup.hp.com with ESMTP (8.7.6/8.7.3) id NAA13980 for ; Tue, 16 Nov 1999 13:43:12 -0800 (PST) Sender: frowand@cup.hp.com Message-ID: <3831CFF0.F4B3CE3E@hp.com> Date: Tue, 16 Nov 1999 13:43:12 -0800 From: Frank Rowand Reply-To: frowand@cup.hp.com MIME-Version: 1.0 To: parisc-linux@thepuffingroup.com Subject: Re: [parisc-linux] depi? References: <199911150736.XAA14959@opus.allegro.com> <19991115092549.G30917@mathe.stud.uni-erlangen.de> <383093DE.A8B73CE4@hp.com> <19991116170819.B750@mathe.stud.uni-erlangen.de> Content-Type: text/plain; charset=us-ascii List-ID: Philipp Rumpf wrote: > > > This is just one of several recent messages dealing with the issues caused by > > locating the kernel at virtual address 0xc0000000 instead of 0x00000000. I > > still don't understand why the kernel can't be at zero, even though several > > people have tried to explain it to me. Can anyone provide a clear > > explanation? > > Advantages of mapping the kernel at 0xc000 0000 (or 0x8000 0000/0xe000 0000) > < stuff deleted > > > Disadvantages > - C code that needs to run in real mode seems to be rather fragile, given Paul's recent experience with head.c. (I think it was Paul.) - A single instance of code can't (easily) be coded to be able to run both in real mode and in virtual mode. - It's real easy to mis-code real mode assembly (eg. use the PA() macro when it shouldn't be used or don't use it when it should be used). - Issues with coherent I/O. < stuff deleted > -Frank