1.\" 2.\" Copyright (c) 2026 Christos Longros <chris.longros@gmail.com> 3.\" 4.\" SPDX-License-Identifier: BSD-2-Clause 5.\" 6.Dd March 21, 2026 7.Dt VMGENC 4 8.Os 9.Sh NAME 10.Nm vmgenc 11.Nd ACPI virtual machine generation ID counter 12.Sh SYNOPSIS 13.Cd device vmgenc 14.Pp 15In 16.Xr loader.conf 5 : 17.Cd vmgenc_load="YES" 18.Sh DESCRIPTION 19The 20.Nm 21driver provides support for the Virtual Machine Generation ID, 22a 128-bit unique identifier exposed by the hypervisor via ACPI. 23The hypervisor changes this identifier whenever the virtual machine 24is cloned, restored from a snapshot, or otherwise duplicated. 25.Pp 26When a generation ID change is detected, the 27.Nm 28driver feeds the new identifier into the kernel entropy pool via 29.Xr random 4 , 30ensuring that duplicated virtual machines do not share 31cryptographic state. 32The driver also sends a 33.Xr devctl 4 34event and an internal kernel notification so that other subsystems 35can respond to the duplication. 36.Pp 37The Virtual Machine Generation ID specification is supported by 38QEMU, VMware ESXi, Microsoft Hyper-V, and Xen. 39.Sh SYSCTL VARIABLES 40The following variable is available: 41.Bl -tag -width indent 42.It Va dev.vmgenc.%d.guid 43The current cached VM generation counter as a 128-bit value. 44This value is updated each time the hypervisor signals a 45generation change. 46.El 47.Sh SEE ALSO 48.Xr acpi 4 , 49.Xr random 4 50.Sh HISTORY 51The 52.Nm 53driver first appeared in 54.Fx 13.0 . 55.Sh AUTHORS 56The 57.Nm 58driver was written by 59.An Conrad Meyer Aq Mt cem@FreeBSD.org . 60.Pp 61This manual page was written by 62.An Christos Longros Aq Mt chris.longros@gmail.com . 63