On Thu, 2016-03-10 at 09:56 +0000, Daniel P. Berrange wrote:
So, I've just seen that QEMU has decided that as of QEMU 2.6, the virt machine type will start to be versioned. This is quite convenient I think as it gives us a nice thing to hook on. ie we see a non-versioned machine type of 'virt' then we use virtio-mmio addressing, however, if we see a versioned virt-X.Y.Z machine type, then we can assume pci by default.
Since the long term plan for AArch64 is to use PCI for everything, this gives us nice default behaviour from this point onwards, while not breaking compatibility for existing early adopters.
Of course people with "legacy" mmio-only guests will stll have a little pain to run then on new QEMU, but honestly I think that's worth it since it will avoid us long term pain in the world where aarch64 uses pci for everything
I think it's way too early to flip the switch and default to PCI addresses: my understanding is that guest OS support is expected to be spotty at best for at least a couple more years. Cheers. -- Andrea Bolognani Software Engineer - Virtualization Team