On 2011-01-18 16:48, Anthony Liguori wrote: > On 01/18/2011 09:43 AM, Jan Kiszka wrote: >> On 2011-01-18 16:04, Anthony Liguori wrote: >> >>> On 01/18/2011 08:28 AM, Jan Kiszka wrote: >>> >>>> On 2011-01-12 11:31, Jan Kiszka wrote: >>>> >>>> >>>>> Am 12.01.2011 11:22, Avi Kivity wrote: >>>>> >>>>> >>>>>> On 01/11/2011 03:54 PM, Anthony Liguori wrote: >>>>>> >>>>>> >>>>>>> Right, we should introduce a KVMBus that KVM devices are created on. >>>>>>> The devices can get at KVMState through the BusState. >>>>>>> >>>>>>> >>>>>> There is no kvm bus in a PC (I looked). We're bending the device model >>>>>> here because a device is implemented in the kernel and not in >>>>>> userspace. An implementation detail is magnified beyond all proportions. >>>>>> >>>>>> An ioapic that is implemented by kvm lives in exactly the same place >>>>>> that the qemu ioapic lives in. An assigned pci device lives on the PCI >>>>>> bus, not a KVMBus. If we need a pointer to KVMState, then we must find >>>>>> it elsewhere, not through creating imaginary buses that don't exist. >>>>>> >>>>>> >>>>>> >>>>> Exactly. >>>>> >>>>> So we can either "infect" the whole device tree with kvm (or maybe a >>>>> more generic accelerator structure that also deals with Xen) or we need >>>>> to pull the reference inside the device's init function from some global >>>>> service (kvm_get_state). >>>>> >>>>> >>>> Note that this topic is still waiting for good suggestions, specifically >>>> from those who believe in kvm_state references :). This is not only >>>> blocking kvmstate merge but will affect KVM irqchips as well. >>>> >>>> It boils down to how we reasonably pass a kvm_state reference from >>>> machine init code to a sysbus device. I'm probably biased, but I don't >>>> see any way that does not work against the idea of confining access to >>>> kvm_state or breaks device instantiation from the command line or a >>>> config file. >>>> >>>> >>> A KVM device should sit on a KVM specific bus that hangs off of sysbus. >>> It can get to kvm_state through that bus. >>> >>> That bus doesn't get instantiated through qdev so requiring a pointer >>> argument should not be an issue. >>> >>> >> This design is in conflict with the requirement to attach KVM-assisted >> devices also to their home bus, e.g. an assigned PCI device to the PCI >> bus. We don't support multi-homed qdev devices. >> > > With vfio, would an assigned PCI device even need kvm_state? IIUC: Yes, for establishing the irqfd link. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
