On Tue, 9 Jun 2020 18:05:59 +0200 Cornelia Huck <coh...@redhat.com> wrote:
> > > > do we really have that many incompatible devices? > > Which devices are compatible in the end? It seems the only ones that > are known to be working are virtio-ccw devices with IOMMU_PLATFORM on. > virtio-pci devices and non-virtio ccw (vfio-ccw, 3270) seem to be out, > as far as I understand it. What about non-ccw? PCI in general, vfio-ap? AFAIU the situation is somewhat complicated. Only virtio devices have the notion of indicating and the duty to indicate access restrictions. We as hypervisor need to prevent the inconsistency where: * the VM is prot virt * the guest can detect that it is running with prot virt using the UV call interface * and the virtio devices emulated by us (QEMU) lie that memory access by the device is not restricted (F_ACCESS_PLATFORM not offered). It is unfortunate that the consequences are this severe, but it is the responsibility to drive the devices accordingly if prot virt is detected. If the guest does this, then s270 and vfio-ccw should work. The problem is, that currently Linux is verifiedly doing the thing only for virtio-ccw. Regards, Halil