> That's not spec, that's linux driver. The spec is the source of truth.
Right, lets follow this. I'm looking at https://docs.oasis-open.org/virtio/virtio/v1.3/csd01/virtio-v1.3-csd01.html Is that correct? That document does not have a definition of word. However, what is interesting is section "4.2.2 MMIO Device Register Layout" DeviceFeaturesSel 0x014 Device (host) features word selection. Writing to this register selects a set of 32 device feature bits accessible by reading from DeviceFeatures. and DriverFeaturesSel 0x024 Activated (guest) features word selection Writing to this register selects a set of 32 activated feature bits accessible by writing to DriverFeatures. I would interpret this as meaning a feature word is a u32. Hence a DWORD is a u64, as the current code uses. Andrew
