On Mon, Apr 08, 2013 at 10:37:45PM +0300, Michael S. Tsirkin wrote: > On Mon, Apr 08, 2013 at 03:32:07PM -0400, Laine Stump wrote: > > On 04/08/2013 12:48 PM, Daniel P. Berrange wrote: > > > On Mon, Apr 08, 2013 at 12:37:49PM -0400, Laine Stump wrote: > > >> I think we're starting to get closer to the concrete problem that's > > >> bothering me. As I understand it (and again - "what I understand" has > > >> repeatedly been shown to be incorrect in this thread :-): > > >> > > >> * Ihere are multiple different types of devices that provide a bus with > > >> 1 or more "slots" that PCI devices (e.g., the virtio-net-pci device, the > > >> e1000 network device, etc) can be plugged into. > > >> > > >> * In the config for those devices, there is a required (auto-generated > > >> if not explicitly provided) <address> element that indicates what > > >> controller that device is plugged into e.g.: > > >> > > >> <interface type='direct'> > > >> ... > > >> <address type='pci' domain='0' bus='0' slot='3' function='0'/> > > >> ... > > >> </interface> > > >> > > >> * domain is always hardcoded to 0, and in the past bus was also always > > >> hardcoded to 0 because until now there has only been a single place > > >> where PCI devices could be connected - the builtin pci.0 bus, which is a > > >> part of the basic "pc" (and some others) virtual machine and provides 32 > > >> slots. > > >> > > >> * Now we are adding the ability to define new PCI buses, for now just a > > >> single kind - a pci-bridge controller, which itself must connect to an > > >> existing PCI slot, and provides 32 new PCI slots. But in the future > > >> there will be more different types of controllers that provide one or > > >> more PCI slots where PCI devices/controllers can be plugged in. > > >> > > >> * In these patches adding support for pci-bridge, we are making the > > >> assumption that there is a 1:1 correspondence between the "index='n'" > > >> attribute of the pci-bridge controller and the "bus='n'" attribute of > > >> the <address> element in devices that will be plugged into that > > >> controller. So for example if we have: > > >> > > >> > > >> <controller type='pci-bridge' index='1'> > > >> <address type='pci' domain='0' bus='0' slot='10' function='0'/> > > >> </controller> > > >> > > >> and then change the <interface> definition above to say "bus='1'", that > > >> interface device will plug into this new bus at slot 3. > > >> > > >> * So let's assume that we add a new controller called "dmi-to-pci-bridge": > > >> > > >> <controller type='dmi-to-pci-bridge' index='0'/> > > >> > > >> Ignoring for now the question of what address we give in the definition > > >> of *this* device (which is itself problematic - do we need a new "pcie" > > >> address type?), if some device is then defined with > > >> > > >> > > >> <address type='pci bus='0' .../> > > >> > > >> How do we differentiate between that meaning "the pci-ptp controller > > >> that is index='0'" and "the pci-bridge controller that is index='0'"? Do > > >> we need to expand our <address> element further? If, as I think you > > >> suggest, we have multiple different kinds of controllers that provide > > >> PCI slots, each with its own namespace, the current pci address element > > >> is inadequate to unambiguously describe where a pci device should be > > >> plugged in. > > > Hmm yes, you're right - as long as we only have <adress type='pci'> > > > then all <controller> elements should use type='pci' too, and we should > > > just distinguish based on the model name of the controller. So ignore > > > my previous suggestion to have 'pci-bridge' and 'pci-root' types, we > > > can only use type='pci' on <controller> elements. > > > > Okay, so that means we preserve the correlation between > > > > <controller type='pci' index='1'> > > > > and > > > > <address type='pci' bus='1' ..../> > > > > > > Should the <controller> device use, e.g. <model type='pci-bridge'/> for > > the model, as is done for <interface> devices? One notable difference is > > that in the case of <interface> (with the exception of "<model > > type='virtio'/>"), the model isn't used for anything except passing > > directly through to qemu (and very recently validating against a list of > > known interface models), while in the case of controllers with > > type='pci', different models will have different rules about what they > > can connect to and what can connect to them, and they will affect what > > is valid in other devices. > > > > An example on a "pc" machinetype that has the builtin PCI bus, one extra > > pci-pci bridge, and an interface device plugged into slot 3 of the > > pci-bridge: > > > > <controller type='pci' index='0'> > > <model type='pci-root'/> <!-- builtin pci bus --> > > </controller> > > <controller type='pci' index='1'> > > <model type='pci-bridge'/> > > </controller> > > <interface type='direct'> > > ... > > <address type='pci' bus='1' slot='3'/> > > </controller> > > > > And for a q35 machinetype that has the root pcie, an i82801b11-bridge > > connected to slot 1e of that, a pci bridge connected to slot 1 of the > > i82801b11-bridge, and an interface plugged into slot 3 of the pci-bridge: > > > > <controller type='pci' index='0'> > > <model type='pcie-root'/> > > </controller> > > <controller type='pci' index='1'> > > <model type='i82801b11-bridge'/> <!-- [*] --> > > <address type='pci' bus='0' slot='0x1e'/> > > </controller> > > <controller type='pci' index='2'> > > <model type='pci-bridge'/> > > <address type='pci' bus='1' slot='1'/> > > </controller> > > <interface type='direct'> > > ... > > <address type='pci' bus='2' slot='3'/> > > </controller> > > > > (note that controllers with model='(pci|pcie)-root' will not have any > > <address> element, because they exist in the basic machine so we don't > > need to connect them to anywhere.) > > > > (also note that it might happen that the bus number in libvirt's config > > will correspond to the bus numbering that shows up in the guest OS, but > > that will just be a happy coincidence) > > > > Does this make sense? > > Confused. So why are you using bus numbers at all? > It's just wrong. They are not wrong. We use to link the <address> element to the <controller> element. Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list