From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757805Ab0FIOXs (ORCPT ); Wed, 9 Jun 2010 10:23:48 -0400 Received: from relay3.sgi.com ([192.48.152.1]:50047 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1757757Ab0FIOXr (ORCPT ); Wed, 9 Jun 2010 10:23:47 -0400 Message-ID: <4C0FA3F0.6040609@sgi.com> Date: Wed, 09 Jun 2010 09:23:44 -0500 From: Mike Habeck User-Agent: Thunderbird 2.0.0.12 (X11/20080226) MIME-Version: 1.0 To: Jesse Barnes Cc: "H. Peter Anvin" , Bjorn Helgaas , Mike Travis , Ingo Molnar , Thomas Gleixner , x86@kernel.org, Jacob Pan , Tejun Heo , LKML , linux-pci@vger.kernel.org Subject: Re: [Patch 1/1] x86 pci: Add option to not assign BAR's if not already assigned References: <4BEAF008.9030805@sgi.com> <201006011649.56074.bjorn.helgaas@hp.com> <4C0608C6.4090901@zytor.com> <201006020945.09107.bjorn.helgaas@hp.com> <4C067D0B.7030804@zytor.com> <20100602085327.71dfaca0@virtuousgeek.org> <4C0EE5FF.5080003@zytor.com> <20100608182633.582fb650@virtuousgeek.org> In-Reply-To: <20100608182633.582fb650@virtuousgeek.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jesse Barnes wrote: > On Tue, 08 Jun 2010 17:53:19 -0700 > "H. Peter Anvin" wrote: > >> On 06/02/2010 08:53 AM, Jesse Barnes wrote: >>>> That's what I thought, which I guess means my original question to Mike >>>> still stands... >>> I thought the whole reason for this was hotplug; we don't want to >>> exhaust I/O space unnecessarily by allocating resources for BARs the >>> BIOS didn't assign so we can keep them around for later hotplug >>> activity. >>> >>> If there's some other issue, it's not too late to drop this patch. >>> >> Okay, now... this means that if a device that the BIOS doesn't know >> about, but which needs I/O addresses, then it will work if hotplugged, >> but not if it is plugged in on system boot? > > Depends on the BIOS interactions on this platform; if the kernel ends > up doing all the allocations itself, we'll allocate space for every BAR > unconditionally, meaning that any hotplugged device should work. Correct, our BIOS allocates I/O space for all devices except for a few that it knows don't use it. On a hotplug attach the kernel will be unconditionally allocating the I/O space for all devices.. The pci=nobar option strictly prevents the kernel from allocating BAR resources to device BARs that the BIOS didn't assign (similar to how the pci=norom option works for the device's ROM BAR) > > But really the SGI guys should comment here. >