Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752441Ab2E3QbM (ORCPT ); Wed, 30 May 2012 12:31:12 -0400 Received: from terminus.zytor.com ([198.137.202.10]:40006 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751655Ab2E3QbK (ORCPT ); Wed, 30 May 2012 12:31:10 -0400 Message-ID: <4FC64B3E.2020002@zytor.com> Date: Wed, 30 May 2012 09:30:54 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1 MIME-Version: 1.0 To: Bjorn Helgaas CC: Steven Newbury , Yinghai Lu , Linus Torvalds , Andrew Morton , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 02/11] PCI: Try to allocate mem64 above 4G at first References: <1337754877-19759-1-git-send-email-yinghai@kernel.org> <20120525193716.GA8817@google.com> <4FC50E09.4000204@zytor.com> <4FC5CEF1.6000509@snewbury.org.uk> In-Reply-To: X-Enigmail-Version: 1.4.1 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 965 Lines: 26 On 05/30/2012 09:27 AM, Bjorn Helgaas wrote: > > You're right, the spec does allow the upper 16 bits of I/O BARs to be > hardwired to zero (PCI spec rev 3.0, p. 226), so this part does make > some sense. I don't think it applies to x86, since I don't think > there's a way to generate an I/O access to anything above 64K, but it > could help other arches. > > I'm inclined to be conservative and wait until we find a problem where > a patch like this would help. > The really conservative thing is to just use 16-bit addresses for I/O on all platforms. I think a lot of non-x86 platforms does that. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/