From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43085) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z5LEI-0005T2-2i for qemu-devel@nongnu.org; Wed, 17 Jun 2015 17:50:43 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Z5LEE-0000OY-Qt for qemu-devel@nongnu.org; Wed, 17 Jun 2015 17:50:42 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42668) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z5LEE-0000OT-9Y for qemu-devel@nongnu.org; Wed, 17 Jun 2015 17:50:38 -0400 Date: Wed, 17 Jun 2015 23:50:33 +0200 From: "Michael S. Tsirkin" Message-ID: <20150617235009-mutt-send-email-mst@redhat.com> References: <20150617155237-mutt-send-email-mst@redhat.com> <20150617141820.GA11337@morn.localdomain> <55818819.3010107@redhat.com> <20150617150544.GA26500@redhat.com> <5581B97E.8020707@redhat.com> <20150617204828-mutt-send-email-mst@redhat.com> <5581C74C.5070405@redhat.com> <20150617192843.GB27117@morn.localdomain> <20150617213011-mutt-send-email-mst@redhat.com> <5581CE07.20302@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5581CE07.20302@redhat.com> Subject: Re: [Qemu-devel] [PATCH v6 7/7] hw/pci-bridge: format SeaBIOS-compliant OFW device node for PXB List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Laszlo Ersek Cc: Marcel Apfelbaum , Kevin O'Connor , qemu-devel@nongnu.org, Markus Armbruster On Wed, Jun 17, 2015 at 09:44:07PM +0200, Laszlo Ersek wrote: > On 06/17/15 21:32, Michael S. Tsirkin wrote: > > On Wed, Jun 17, 2015 at 03:28:44PM -0400, Kevin O'Connor wrote: > >> On Wed, Jun 17, 2015 at 09:15:24PM +0200, Laszlo Ersek wrote: > >>> On 06/17/15 20:54, Michael S. Tsirkin wrote: > >>>> Right. But what I was discussing is a different issue. The point is > >>>> that it does not make sense to have /pci@i0cf8 under two hierarchies: > >>>> it's the same register. What happens is that you access /pci@i0cf8 and > >>>> then *through that* you access another pci root. Not the other way > >>>> around. The proposal thus is to switch to /pci@i0cf8/pci-root@N in > >>>> seabios, > >>> > >>> For me this is still Question 1 -- 'everything in that pattern that is > >>> not "N"'. > >>> > >>> You seem to care about the *semantics* of that OFW device path fragment. > >>> I don't. First, the relevant IEEE spec is prohibitively hard for me to > >>> interpret semantically. Second, there is no known firmware that actually > >>> looks at the "i0cf8" unit-address term and decides *based on that term* > >>> that it has to talk PCI via 0xCF8 and 0xCFC. In other words, the current > >>> second node is entirely opaque in my interpretation. > >>> > >>>> unconditionally - not if (QEMU). > >>> > >>> This might qualify as some kind of semantic cleanup, but it will > >>> nonetheless break the SeaBIOS boot options expressed in OFW notation > >>> that are already persistently stored in cbfs, on physical machines. (As > >>> far as I understood.) It might not break the Coreboot-SeaBIOS interface, > >>> but it might invalidate preexistent entries that exist in the prior form > >>> (wherever they exist on physical hardware). > >>> > >>>> And I thought Kevin agreed > >>>> it's a good idea. > >>>> > >>>> Kevin - is this a good summary of your opinion? > >>> > >>> Kevin, please do answer. > >> > >> It is true that it would "invalidate preexistent entries" for > >> coreboot/seabios users that upgrade, but I think that is manageable. > >> So I defer the syntax discussion and decisions to the QEMU developers > >> that are doing the bulk of the work. > >> > >> -Kevin > > > > I'm fine with either /pci@i0cf8,%x or /pci-root@%x/pci@i0cf8, with a > > slight preference to the later - in particular it's easier > > to implement in QEMU. > > > > It means old bios won't boot from a pxb, but I think that's > > manageable - it works otherwise. > > I don't understand -- the second option you named > ("/pci-root@%x/pci@i0cf8") is what this patch implements, and "old" (ie. > current) SeaBIOS does boot from it. > > Laszlo Ouch. I meant /pci@i0cf8//pci-root@%x. As you see, it's confusing.