virtio-net and virtio-scsi driver didn't work on PowerPC64 due to an endianess problem on Device Configuration Space area. This area was assumed to be in same endianess as the guest OS, but virtio-1.x spec says:
2.3 Device Configuration Space
Device configuration space is generally used for rarely-changing or initialization-time parameters. Where configuration fields are optional, their existence is indicated by feature bits: Future versions of this specification will likely extend the device configuration space by adding extra fields at the tail. Note: **The device configuration space uses the little-endian format for multi-byte fields.**
This patch fixes the endianess on Big Endian platforms such as PowerPC64 and enables it on default kernel configuration.
Reference: http://docs.oasis-open.org/virtio/virtio/v1.0/cs04/virtio-v1.0-cs04.html#x1-170003