| VIORND(4) | Device Drivers Manual | VIORND(4) | 
viornd —
VirtIO entropy source
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.
The viornd driver appeared in OpenBSD
  5.5.
The viornd driver was written by
  Stephan Fritsch
  <sf@fritsch.de> and
  reworked to request entropy upon demand by
Thor Lancelot Simon
  <tls@NetBSD.org>.
VirtIO appears to support at least 8 pending entropy requests, but
  viornd currently supports only one pending request at
  a time.