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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: RFC: PCI devices passthrough on Arm design proposal
> On 17 Jul 2020, at 17:05, Roger Pau Monné <roger.pau@xxxxxxxxxx> wrote: > > On Fri, Jul 17, 2020 at 02:49:20PM +0000, Bertrand Marquis wrote: >> >> >>> On 17 Jul 2020, at 16:41, Roger Pau Monné <roger.pau@xxxxxxxxxx> wrote: >>> >>> On Fri, Jul 17, 2020 at 02:34:55PM +0000, Bertrand Marquis wrote: >>>> >>>> >>>>> On 17 Jul 2020, at 16:06, Jan Beulich <jbeulich@xxxxxxxx> wrote: >>>>> >>>>> On 17.07.2020 15:59, Bertrand Marquis wrote: >>>>>> >>>>>> >>>>>>> On 17 Jul 2020, at 15:19, Jan Beulich <jbeulich@xxxxxxxx> wrote: >>>>>>> >>>>>>> On 17.07.2020 15:14, Bertrand Marquis wrote: >>>>>>>>> On 17 Jul 2020, at 10:10, Jan Beulich <jbeulich@xxxxxxxx> 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? >> >> We will add some new definitions for the ECAM regions in the guest physmap >> declared in xen (include/asm-arm/config.h) > > I think I'm confused, but that file doesn't contain anything related > to the guest physmap, that's the Xen virtual memory layout on Arm > AFAICT? > > Does this somehow relate to the physical memory map exposed to guests > on Arm? Yes it does. We will add new definitions there related to VPCI to reserve some areas for the VPCI ECAM and the IOMEM areas. Bertrand > > Roger.
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