From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:33178) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UhdRF-0004eT-BR for qemu-devel@nongnu.org; Wed, 29 May 2013 06:17:05 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UhdRB-0001J4-EF for qemu-devel@nongnu.org; Wed, 29 May 2013 06:17:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58584) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UhdRB-0001Ib-4l for qemu-devel@nongnu.org; Wed, 29 May 2013 06:16:57 -0400 Date: Wed, 29 May 2013 13:17:13 +0300 From: "Michael S. Tsirkin" Message-ID: <20130529101713.GP4472@redhat.com> References: <1368059472-25071-1-git-send-email-david@gibson.dropbear.id.au> <1368059472-25071-7-git-send-email-david@gibson.dropbear.id.au> <20130523112230.GE17480@redhat.com> <20130523121627.GC26259@boomeroo.fritz.box> <20130529094341.GG5489@boomeroo.fritz.box> <20130529095553.GN4472@redhat.com> <20130529100642.GJ5489@boomeroo.fritz.box> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130529100642.GJ5489@boomeroo.fritz.box> Subject: Re: [Qemu-devel] [PATCH 6/8] pci: Simpler implementation of primary PCI bus List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Gibson Cc: aliguori@us.ibm.com, qemu-devel@nongnu.org, David Gibson On Wed, May 29, 2013 at 08:06:42PM +1000, David Gibson wrote: > On Wed, May 29, 2013 at 12:55:53PM +0300, Michael S. Tsirkin wrote: > > On Wed, May 29, 2013 at 07:43:41PM +1000, David Gibson wrote: > > > On Thu, May 23, 2013 at 10:16:27PM +1000, David Gibson wrote: > > > > On Thu, May 23, 2013 at 02:22:30PM +0300, Michael S. Tsirkin wrote: > > > > > On Thu, May 09, 2013 at 10:31:10AM +1000, David Gibson wrote: > > > > > > Currently pci_get_primary_bus() searches the list of root buses for one > > > > > > with domain 0. But since host buses are always registered with domain 0, > > > > > > this just amounts to finding the only PCI host bus. > > > > > > > > > > > > This simplifies the implementation by defining the primary PCI bus to > > > > > > be the first one registered, using a global variable to track it. > > > > > > > > > > > > Signed-off-by: David Gibson > > > > > > > > > > Or better: can we just fail if there is more than > > > > > one root? > > > > > > > > That might work, I'll look into doing that. > > > > > > So, the difficulty with this is that then any machine with multiple > > > PCI bridges could not use pci_nic_init(), since it calls > > > pci_get_bus_devfn() which calls pci_find_primary_bus() which would > > > always fail. And using pci_nic_init() is more or less mandatory in > > > the machine_init function to support old-style nic configuration. > > > > > > Suggestions? > > > > You mean multiple PCI roots? > > Well, there are no legacy machines with multiple roots to support, are > > there? So why do we need to support legacy flags for these new > > configurations? > > Because people expect them. People can learn, somehow they will learn to add a new root, so they can learn to use -device too. So let's make it fail on multiple roots, and output a message along the lines of "please use -device virtio-net-pci instead". > Plus on spapr we already support the > legacy nic options; it would be very strange for them to suddenly > break when we add a second host bridge. Not sure who "we" is here. IMHO user should ask for a new machine type with two roots explicitly. > -- > David Gibson | I'll have my music baroque, and my code > david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ > | _way_ _around_! > http://www.ozlabs.org/~dgibson