On Fri, Jul 17, 2020 at 02:34:55PM +0000, Bertrand Marquis wrote: > > > > On 17 Jul 2020, at 16:06, Jan Beulich <jbeul...@suse.com> wrote: > > > > On 17.07.2020 15:59, Bertrand Marquis wrote: > >> > >> > >>> On 17 Jul 2020, at 15:19, Jan Beulich <jbeul...@suse.com> wrote: > >>> > >>> On 17.07.2020 15:14, Bertrand Marquis wrote: > >>>>> On 17 Jul 2020, at 10:10, Jan Beulich <jbeul...@suse.com> wrote: > >>>>> On 16.07.2020 19:10, Rahul Singh wrote: > >>>>>> # Emulated PCI device tree node in libxl: > >>>>>> > >>>>>> Libxl is creating a virtual PCI device tree node in the device tree to > >>>>>> enable the guest OS to discover the virtual PCI during guest boot. We > >>>>>> introduced the new config option [vpci="pci_ecam"] for guests. When > >>>>>> this config option is enabled in a guest configuration, a PCI device > >>>>>> tree node will be created in the guest device tree. > >>>>> > >>>>> I support Stefano's suggestion for this to be an optional thing, i.e. > >>>>> there to be no need for it when there are PCI devices assigned to the > >>>>> guest anyway. I also wonder about the pci_ prefix here - isn't > >>>>> vpci="ecam" as unambiguous? > >>>> > >>>> This could be a problem as we need to know that this is required for a > >>>> guest upfront so that PCI devices can be assigned after using xl. > >>> > >>> I'm afraid I don't understand: When there are no PCI device that get > >>> handed to a guest when it gets created, but it is supposed to be able > >>> to have some assigned while already running, then we agree the option > >>> is needed (afaict). When PCI devices get handed to the guest while it > >>> gets constructed, where's the problem to infer this option from the > >>> presence of PCI devices in the guest configuration? > >> > >> If the user wants to use xl pci-attach to attach in runtime a device to a > >> guest, this guest must have a VPCI bus (even with no devices). > >> If we do not have the vpci parameter in the configuration this use case > >> will not work anymore. > > > > That's what everyone looks to agree with. Yet why is the parameter needed > > when there _are_ PCI devices anyway? That's the "optional" that Stefano > > was suggesting, aiui. > > I agree in this case the parameter could be optional and only required if not > PCI device is assigned directly in the guest configuration.
Where will the ECAM region(s) appear on the guest physmap? Are you going to re-use the same locations as on the physical hardware, or will they appear somewhere else? Roger.
