vmgenc4
Acpi virtual machine generation id counter
Usage
device vmgenc
In loader.conf(5): vmgenc_load="YES"
Overview
The vmgenc driver provides support for the Virtual Machine Generation ID, a 128-bit unique identifier exposed by the hypervisor via ACPI. The hypervisor changes this identifier whenever the virtual machine is cloned, restored from a snapshot, or otherwise duplicated.
When a generation ID change is detected, the vmgenc driver feeds the new identifier into the kernel entropy pool via random(4), ensuring that duplicated virtual machines do not share cryptographic state. The driver also sends a devctl(4) event and an internal kernel notification so that other subsystems can respond to the duplication.
The Virtual Machine Generation ID specification is supported by QEMU, VMware ESXi, Microsoft Hyper-V, and Xen.
Sysctl variables
The following variable is available:
- dev.vmgenc.%d.guid
-
The current cached VM generation counter as a 128-bit value. This value is updated each time the hypervisor signals a generation change.
Releases
Unchanged in 3 releases since FreeBSD 14.5-RELEASE.