On Wed, Sep 10, 2014 at 8:36 AM, Christopher Covington <cov@xxxxxxxxxxxxxx> wrote: > On 09/04/2014 10:57 PM, Andy Lutomirski wrote: >> There's a third option: try to make virtio-mmio work everywhere >> (except s390), at least in the long run. This other benefits: it >> makes minimal hypervisors simpler, I think it'll get rid of the limits >> on the number of virtio devices in a system. ARM is already going >> this direction, and I imagine that PPC support would be >> straightforward (it's already using devicetree). > > In my opinion, a uniform "virt" machine for every instruction set would be > very beneficial. I would guess that MMIO is more universally available than > PCI, and as you point out, simpler to implement. Except for x86 :( That's presumably fixable, though. > >> Does virtio-mmio have any reasonable way of doing hotplug? It could >> also eventually make sense to have a standard for virtio on virtio. > > I don't think so, but it seems possible. My bystander understanding is that > QEMU allocates some fixed number of VirtIO-MMIO devices, maybe a dozen, in the > device tree. The ones that don't actually get hooked up to something real like > a block device or network interface are populated with a dummy device. One > naive approach might be to allow the dummy devices to tell the kernel that > they are now changing to a real device. My thought (which I completely failed to articulate) was to have a spec for a virtio device that exposes a complete virtio bus along with hotplug and per-cpu interrupts (a la MSI-X). This might be a bit complicated, but it would work everywhere without any firmware or platform issues. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
