From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 21 May 2001 07:23:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 21 May 2001 07:23:24 -0400 Received: from penguin.e-mind.com ([195.223.140.120]:8454 "EHLO penguin.e-mind.com") by vger.kernel.org with ESMTP id ; Mon, 21 May 2001 07:23:07 -0400 Date: Mon, 21 May 2001 13:19:59 +0200 From: Andrea Arcangeli To: "David S. Miller" Cc: Andrew Morton , Ivan Kokshaysky , Richard Henderson , linux-kernel@vger.kernel.org Subject: Re: alpha iommu fixes Message-ID: <20010521131959.M30738@athlon.random> In-Reply-To: <20010520163323.G18119@athlon.random> <15112.26868.5999.368209@pizda.ninka.net> <20010521034726.G30738@athlon.random> <15112.48708.639090.348990@pizda.ninka.net> <20010521105944.H30738@athlon.random> <15112.55709.565823.676709@pizda.ninka.net> <20010521115631.I30738@athlon.random> <15112.59880.127047.315855@pizda.ninka.net> <20010521125032.K30738@athlon.random> <15112.62766.368436.236478@pizda.ninka.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <15112.62766.368436.236478@pizda.ninka.net>; from davem@redhat.com on Mon, May 21, 2001 at 03:59:58AM -0700 X-GnuPG-Key-URL: http://e-mind.com/~andrea/aa.gnupg.asc X-PGP-Key-URL: http://e-mind.com/~andrea/aa.asc Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 21, 2001 at 03:59:58AM -0700, David S. Miller wrote: > This still leaves around 800MB IOMMU space free on that sparc64 PCI > controller. if it was 400mbyte you were screwed up too, the point here is that the marging is way too to allows ignore the issue completly, furthmore there can be fragmentation effects in the pagetbles, at least in the way alpha manages them which is to find contigous virtual pci bus addresses for each sg. Alpha in mainline is just screwedup if a single pci bus tries to dynamic map more than 128mbyte, changing it to 512mbyte is trivial, growing more has performance implications as it needs to reduce the direct windows which I don't like to as it would also increase the number of machines that will get bitten by drivers that still use the virt_to_bus and also increase the pressure on the iommu ptes too. Now I'm not asking to break the API for 2.4 to take care of that, you seems to be convinced in fixing this for 2.5 and I'm ok with that, I just changed the printk of running out of entries to be KERN_ERR at least, so we know if somebody has real life troubles with 2.4 I will go HIGHMEM which is a matter of 2 hours for me to implement. Only thing I suggest is to change the API before starting fixing the drivers, I mean: don't start checking for bus address 0 before changing the API to return faliure in another way. It's true x86 is reserving the zero page anyways because it's a magic bios thing, but for example on the alpha such a 0 bus address that we cannot use wastes 8 mbyte of DMA virtual bus addresses that we reserve for the ISA cards (of course we almost never need 16mbyte of ram all under isa dma but since it's so low cost to allow that I think we will just in case). Andrea