George Dunlap writes ("RFC: Automatically making a PCI device assignable in the
config file"):
I've been doing some work to try to make driver domains easier to set
up and use. At the moment, in order to pass a device through to a
guest, you first need to assign it to pciback. This involves doing
one of three things:
* Running xl pci-assignable-add for the device
* Specifying the device to be grabbed on the dom0 Linux command-line
* Doing some hackery in /etc/modules.d
None of these are very satisfying. What I think would be better is if
there was a way to specify in the guest config file, "If device X is
not assignable, try to make it assignable". That way you can have a
driver domain grab the appropriate device just by running "xl create
domnet"; and once we have the xendomains script up and running with
xl, you can simply configure your domnet appropriately, and then put
it in /etc/xen/auto, to be started automatically on boot.
My initial idea was to add a parameter to the pci argument in the
config file; for example:
pci = ['08:04.1,permissive=1,seize=1']
The 'seize=1' would indicate that if bdf 08:04.1 is not already
assignable, that xl should try to make is assignable.
I think it's a design error that this isn't done automatically by
default.
It would be nice if there was a safety check that the device isn't
currently in use by dom0, but I don't think it's essential. We could
just put a note in the docs saying "if you specify your dom0 nic it
will go away, duh" or something.
