So, from a qemu command line perspective, all you should have to do is
pass qemu the device-tree -path- to the device you want to pass-trough
(you may support passing a full hierarchy here).
I agree in principle but I think it should be done in a slightly
different way.
I think we ought to support composing a device by passthrough. For
instance, something like:
[physical-device "mydev"]
region[0].file = "/dev/mem"
region[0].guest_address = "0x42232000"
region[0].file_offset = "0x23423400"
region[0].size = "4096"
irq[0].guest_irq = "10"
irq[0].host_irq = "10"
This should be independent of anything to do with device tree. This
would be useful for x86 too to assign platform devices (like the HPET).
I'm not quite sure what you're getting at here. IMO there should be little or
no need for special knowledge of passthrough devices. They should just be
annother qdev device, configured in the normal way. e.g.:
-device sysbus-host,hostdev=whatever,normal_mmio_and_irq_config
I think there should be a separate mechanism to manipulate the guest
device tree, just like there are mechanisms to manipulate the guest's
ACPI tables.
I aggree. Any sort of device tree (IIUC ACPI tables are in principle giving
the same information) is, in practice, going to need to be assembled at
runtime. This needs some mechanism for devices to describe themselves,
probably largely independent of actual machine/device creation code.
We've got away without it thus far because the only real place where we have
nontrivial user-specified machine variants is on the PCI bus. Devices there
are for the most part self-describing so the guest firmware/OS can probe
hardware itself.
Paul