Kernel Interfaces Manual
NAME viornd — VirtIO entropy source
SYNOPSIS viornd* at virtio?
DESCRIPTION When the system has entropy demand, the viornd driver, used with a compatible hypervisor such as QEMU, KVM, or Google Compute Engine, requests entropy using the VirtIO random number interface and feeds it into the system entropy pool.
HISTORY The viornd driver appeared in OpenBSD 5.5.
CAVEATS VirtIO appears to support at least 8 pending entropy requests, but viornd currently supports only one pending request at a time.