[Virtio-fs] [virtiofsd] Issue opened: Implement VHOST_USER_SLAVE_FS_IO

[virtiofs-bot at sinrega.org]

The DAX support is only partial at the moment, as a complete support of this feature expects the command `VHOST_USER_SLAVE_FS_IO` to be honored.
Without this command, the guest might expect the backend to access some non-guest memory ranges, which it won't be able to do without this extra command.

Reference: https://gitlab.com/virtio-fs/virtiofsd/-/issues/39 and https://github.com/cloud-hypervisor/cloud-hypervisor/issues/3869
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https://gitlab.com/virtio-fs/virtiofsd/-/issues/41