Re: [libvirt] new libvirt "pci" controller type and pcie/q35 (was Re: [PATCH 4/7] add pci-bridge controller type)

On 04/15/2013 06:14 PM, Don Dutile wrote: > On 04/15/2013 04:09 PM, Laine Stump wrote: >> On 04/15/2013 06:29 AM, Daniel P. Berrange wrote: >>> On Fri, Apr 12, 2013 at 11:46:15AM -0400, Laine Stump wrote: >>>> On 04/11/2013 07:23 AM, Michael S. Tsirkin wrote: >>>>> On Thu, Apr 11, 2013 at 07:03:56AM -0400, Laine Stump wrote: >>>>>> On 04/10/2013 05:26 AM, Daniel P. Berrange wrote: >>>>>>>>> So if we later allowed for mutiple PCI roots, then we'd have >>>>>>>>> something >>>>>>>>> like >>>>>>>>> >>>>>>>>> <controller type="pci-root" index="0"> >>>>>>>>> <model name="i440FX"/> >>>>>>>>> </controller> >>>>>>>>> <controller type="pci-root" index="1"> >>>>>>>>> <model name="i440FX"/> >>>>>>>>> </controller> >>>>>>>>> <controller type="pci" index="0"> <!-- Host bridge 1 --> >>>>>>>>> <address type='pci' domain='0' bus='0' slot='0''/> >>>>>>>>> </controller> >>>>>>>>> <controller type="pci" index="0"> <!-- Host bridge 2 --> >>>>>>>>> <address type='pci' domain='1' bus='0' slot='0''/> >>>>>>>>> </controller> >>>> >>>> There is a problem here - within a given controller type, we will now >>>> have the possibility of multiple controllers with the same index - the >>>> differentiating attribute will be in the<address> subelement, which >>>> could create some awkwardness. Maybe instead this should be handled >>>> with >>>> a different model of pci controller, and we can add a "domain" >>>> attribute >>>> at the toplevel rather than specifying an<address>? >>> IIUC there is a limit on the number of PCI buses you can create per >>> domain, due to fixed size of PCI addresses. Google suggests to me >>> the limit is 256. So for domain 1, we could just start index at >>> 256, and domain 2 at 512, etc >> >> Okay. Whether we choose that method, or a separate domain attribute, I'm >> satisfied that we'll be able to find a way to solve it when the time >> comes (and it hasn't yet), so we can ignore that problem for now. >> >> > *PLEASE* don't create a new/competing naming/numbering scheme for > differentiating > PCI domains.... as much as I dislike the overuse of the term 'domain', > it's what > is used. No sane person is going to look to assign PCI bus numbers > > 256 in order > to get new/different domains. > The name sucks, but that's what it's called in the code, and what > customers are use to I infer from this that you're okay with: <controller type='pci' domain='n' index='n'> when defining a new controller (using "index" instead of "bus" is a bit bothersome, but it is following current convention; should we reconsider and just call it "bus" this time?), and: