Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752813Ab2E3Qer (ORCPT ); Wed, 30 May 2012 12:34:47 -0400 Received: from mail-wg0-f44.google.com ([74.125.82.44]:38932 "EHLO mail-wg0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752212Ab2E3Qep convert rfc822-to-8bit (ORCPT ); Wed, 30 May 2012 12:34:45 -0400 MIME-Version: 1.0 In-Reply-To: References: <1337754877-19759-1-git-send-email-yinghai@kernel.org> <20120525043651.GA1391@google.com> <20120525193716.GA8817@google.com> <4FC50E09.4000204@zytor.com> <4FC5CEF1.6000509@snewbury.org.uk> From: Linus Torvalds Date: Wed, 30 May 2012 09:33:00 -0700 X-Google-Sender-Auth: qh-tNfBmpgKx-R23__q4wZyMvnQ Message-ID: Subject: Re: [PATCH 02/11] PCI: Try to allocate mem64 above 4G at first To: Bjorn Helgaas Cc: Steven Newbury , Yinghai Lu , "H. Peter Anvin" , Andrew Morton , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1302 Lines: 30 On Wed, May 30, 2012 at 9:27 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. I agree. I would be *very* suspicious of "it might help with other architectures". Sure, other architectures might be using non-16-bit IO addresses for their motherboard resources (just because they can). However, any hotplug device is most likely (by far) to have been tested and designed for x86, which means that even if it might look like it has more than 16 bits of IO space, it will never have been tested that way. So rather than make it likely to help other architectures, I'd say that it would make it likely to break things. Linus -- 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/