Description

Currently, the drivers are implementing a strict barrier for guest-to-host communication and do not have a VIRTIO_F_ORDER_PLATFORM flag.

Some HW have already implemented the VIRTIO_F_ORDER_PLATFORM flag and expect the guest to use this feature.

As a first stage, patches are being submitted upstream (like: https://github.com/virtio-win/kvm-guest-drivers-windows/pull/1147) to ack the feature. 

But the drivers are not really relaxing barriers when acking VIRTIO_F_ORDER_PLATFORM. This behavior should be implemented to improve the drivers' performance when working with real HW. 

What SSTs and Layered Product teams should review this?