Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753992Ab3F0NGL (ORCPT ); Thu, 27 Jun 2013 09:06:11 -0400 Received: from mga14.intel.com ([143.182.124.37]:8169 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752902Ab3F0NGI (ORCPT ); Thu, 27 Jun 2013 09:06:08 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.87,952,1363158000"; d="scan'208";a="260896702" Date: Thu, 27 Jun 2013 16:09:40 +0300 From: Mika Westerberg To: Alex Williamson Cc: Bjorn Helgaas , Jesse Barnes , Greg Kroah-Hartman , "Rafael J. Wysocki" , Yinghai Lu , "Ronciak, John" , "Penner, Miles J" , Bruce Allan , "Kirill A. Shutemov" , Heikki Krogerus , "linux-kernel@vger.kernel.org" , "linux-pci@vger.kernel.org" , "x86@kernel.org" Subject: Re: [PATCH 6/6] x86/PCI: quirk Thunderbolt PCI-to-PCI bridges Message-ID: <20130627130940.GV9294@intel.com> References: <1372177330-28013-1-git-send-email-mika.westerberg@linux.intel.com> <1372177330-28013-7-git-send-email-mika.westerberg@linux.intel.com> <20130625141556.2f9de7b1@jbarnes-desktop> <20130626121757.GP9294@intel.com> <1372284901.30572.625.camel@ul30vt.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1372284901.30572.625.camel@ul30vt.home> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2423 Lines: 50 On Wed, Jun 26, 2013 at 04:15:01PM -0600, Alex Williamson wrote: > On Wed, 2013-06-26 at 14:59 -0600, Bjorn Helgaas wrote: > > [+cc Alex] > > > > On Wed, Jun 26, 2013 at 6:17 AM, Mika Westerberg > > wrote: > > > On Tue, Jun 25, 2013 at 02:15:56PM -0700, Jesse Barnes wrote: > > >> On Tue, 25 Jun 2013 19:22:10 +0300 > > >> Mika Westerberg wrote: > > >> > > >> > + if (!(pci_probe & PCI_NOASSIGN_ROMS)) { > > >> > + pr_info("Thunderbolt host router detected disabling ROMs\n"); > > >> > + pci_probe |= PCI_NOASSIGN_ROMS; > > >> > + } > > >> > > >> I wonder if this should just be the default on x86? Or do we allocate > > >> ROM space to address some other platform where we need it and the BIOS > > >> doesn't do it for the devices we care about? > > > > > > Good question. In our case it definitely helps to have pci=norom the > > > default. Can't tell if it might break something that depends on the current > > > behaviour. > > > > I think the current default behavior is that if the BIOS has assigned > > the ROM BAR, we keep that assignment, and if it hasn't, we allocate > > MEM space for it. And "pci=norom" means that we don't allocate MEM > > space for it, even if the BIOS hasn't assigned it. > > > > "pci=norom" is only implemented on x86. I think most other arches > > allocate MEM space for ROMs, with no way to turn that off. PA-RISC > > seems to ignore ROMs (dino_fixup_bus()), but that looks like the > > exception. > > > > I'm slightly concerned that if we make the x86 default be "never > > assign space for ROMs unless the BIOS has done it," we might break > > virtualized guests that need access to ROMs. Alex? > > Yep, I'm more than slightly concerned by that too. Whenever possible we > want to pass the ROM to the guest since it may end up being a boot > device or drivers within the guest may require it. We can pass the ROM > to the guest from an image file, but that requires someplace from which > to dump the image, which is usually PCI sysfs. Thanks, OK, then I guess changing the default is out of the question. We don't want to break things. -- 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/