On 1/14/22 21:31, Matthew Rosato wrote:
Enable interpretive execution of zPCI instructions + adapter interruption forwarding for s390x KVM vfio-pci. This is done by introducing a series of new vfio-pci feature ioctls that are unique vfio-pci-zdev (s390x) and are used to negotiate the various aspects of zPCI interpretation setup. By allowing intepretation of zPCI instructions and firmware delivery of interrupts to guests, we can significantly reduce the frequency of guest SIE exits for zPCI. We then see additional gains by handling a hot-path instruction that can still intercept to the hypervisor (RPCIT) directly in kvm. From the perspective of guest configuration, you passthrough zPCI devices in the same manner as before, with intepretation support being used by default if available in kernel+qemu. Will reply with a link to the associated QEMU series.
I did the comment in a patch but I think that centralizing it here is clearer: I think having a documentation in Documentation/S390 like we have already for VFIO AP and VFIO CCW would be a good thing.
-- Pierre Morel IBM Lab Boeblingen
