On 08.07.2013, at 15:08, Peter Maydell wrote: > On 8 July 2013 13:59, Alexander Graf <ag...@suse.de> wrote: >> On 08.07.2013, at 14:57, Alexander Graf wrote: >>> On 27.06.2013, at 15:04, Peter Maydell wrote: >>>> The basic idea is that the board instantiates some transports, >>> >>> I really dislike that idea. Couldn't you also create a new >>> bus for your vexpress platform and add a virtio-mmio-vexpress >>> device that automatically allocates an interrupt from the main >>> PIC on instantiation? That way you could create transports >>> using -device. > > This doesn't seem to gain anything except that the user has > to use -device twice rather than once.
Yes, it does. You can have other devices than just virtio ones on those IRQ lines. Assigned devices for example. > >>> Combine that with automatic fdt generation and you get fully >>> command line scaling device creation. >> >> Ah, you already have the fdt generation bit. So you're really >> only missing the automatic irq allocation to make it actually >> user friendly and flexible. > > It's not clear to me how you can automatically allocate an IRQ: > there just aren't that many available, and I'm already a bit For a first draft, how about your allocator returns those 4 consecutively? For the PV machine things will become more obvious. Maybe we could even share the same bus type between your PV machine, vexpress and the e500 machines? > nervous about stealing 4, because we might run into issues if > newer versions of h/w use those IRQs for something else. One > approach would be to have all virtio transports share an IRQ > line (the spec currently forbids this; I need to test if it > would actually work in practice...) > > As far as I know there's no way to find out at board > construction how many virtio devices you might want. Hence you shouldn't create them :). Alex
