On Fri, 5 Jun 2020 12:45:35 +0200 Cornelia Huck <cohuck@xxxxxxxxxx> wrote: > On Thu, 21 May 2020 13:43:04 +1000 > David Gibson <david@xxxxxxxxxxxxxxxxxxxxx> wrote: > > > The default behaviour for virtio devices is not to use the platforms normal > > DMA paths, but instead to use the fact that it's running in a hypervisor > > to directly access guest memory. That doesn't work if the guest's memory > > is protected from hypervisor access, such as with AMD's SEV or POWER's PEF. > > > > So, if a guest memory protection mechanism is enabled, then apply the > > iommu_platform=on option so it will go through normal DMA mechanisms. > > Those will presumably have some way of marking memory as shared with the > > hypervisor or hardware so that DMA will work. > > cc: Halil, who had been looking at the interaction of virtio-ccw > devices and s390 protected virt. > > (IIRC, we wanted to try with a on/off/auto property for virtio-ccw?) Thanks Connie! I will definitely look into this. And regarding on/off/auto I will try to send out something today. Regards, Halil
