From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37754) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WXCJ8-0008Hl-PW for qemu-devel@nongnu.org; Mon, 07 Apr 2014 12:22:08 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WXCJ2-000378-KX for qemu-devel@nongnu.org; Mon, 07 Apr 2014 12:22:02 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48155) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WXCJ2-00036y-BI for qemu-devel@nongnu.org; Mon, 07 Apr 2014 12:21:56 -0400 Date: Mon, 7 Apr 2014 19:22:34 +0300 From: "Michael S. Tsirkin" Message-ID: <20140407162234.GD17277@redhat.com> References: <1396868342-12005-1-git-send-email-marcel.a@redhat.com> <20140407121508.GD16369@redhat.com> <1396874646.5001.76.camel@nilsson.home.kraxel.org> <20140407133415.GB16541@redhat.com> <1396878714.10570.18.camel@localhost.localdomain> <20140407140901.GB16907@redhat.com> <1396880173.10570.25.camel@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1396880173.10570.25.camel@localhost.localdomain> Subject: Re: [Qemu-devel] [SeaBIOS] [PATCH] hw/pci: reserve IO and mem for pci-2-pci bridges with no devices attached List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Marcel Apfelbaum Cc: kevin@koconnor.net, seabios@seabios.org, Gerd Hoffmann , qemu-devel@nongnu.org On Mon, Apr 07, 2014 at 05:16:13PM +0300, Marcel Apfelbaum wrote: > On Mon, 2014-04-07 at 17:09 +0300, Michael S. Tsirkin wrote: > > On Mon, Apr 07, 2014 at 04:51:54PM +0300, Marcel Apfelbaum wrote: > [...] > > > > > I don't think we'll need that for the SHPC bridge. > > > > > > > > Why not? > > > Because "has shpc" => not an PCIe port. (as far as I know) > > > Anyway, why have shpc capability but no I/O or mem to support it? > ^^^ > [...] > > > > > > AFAIK the spec does not list reset value for this register. > > IIRC QEMU resets both to 0. > Thanks, what do you think about the above ? ^^^ > While I am not against it, it seems redundant. > It has shpc => it needs I/O or mem space. > > Marcel Fair enough but it can have shpc and memory without io, or shpc and io without memory. > > > > > > > > - read back value > > > > > > > > value 0 means bridge does not support I/O. > > > > > > > > > > > > A similar trick should work for other optional resources. > > > > > > > > > > > > > For express it indeed makes sense to avoid claiming IO address space. > > > > > I'd try to find something more automatic though, where you don't need > > > > > some kind of "disable io for this express port" config option. > > > > > > > > Won't same trick as above work? > > > > > > > > > For express ports which can only have a single device underneath we can > > > > > check whenever we have a device and if one is present already don't > > > > > bother claiming extra resources for hotplug. > > > > > > > > > > > > + for (cap = pci_config_readb(pci->bdf, PCI_CAPABILITY_LIST); cap; > > > > > > > + cap = pci_config_readb(pci->bdf, cap + PCI_CAP_LIST_NEXT)) > > > > > > > + if (pci_config_readb(pci->bdf, cap + PCI_CAP_LIST_ID) == cap_id) > > > > > > > + return cap; > > > > > > > > > > > > I would also limit this to 256 iterations, to make sure > > > > > > we dont' get into an infinite loop with a broken device. > > > > > > > > > > Good point. > > > > > > > > > > cheers, > > > > > Gerd > > > > > > > > > > > > >