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. 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
