From: Ben Warren <b...@skyportsystems.com> Signed-off-by: Ben Warren <b...@skyportsystems.com> Cc: Gal Hammer <gham...@redhat.com> --- docs/specs/vmgenid.txt | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) create mode 100644 docs/specs/vmgenid.txt
diff --git a/docs/specs/vmgenid.txt b/docs/specs/vmgenid.txt new file mode 100644 index 0000000..afc1717 --- /dev/null +++ b/docs/specs/vmgenid.txt @@ -0,0 +1,38 @@ +VIRTUAL MACHINE GENERATION ID +============================= + +Copyright (C) 2016 Red Hat, Inc. +Copyright (C) 2016 Skyport Systems, Inc. + +This work is licensed under the terms of the GNU GPL, version 2 or later. +See the COPYING file in the top-level directory. + +=== + +The VM generation ID (vmgenid) device is an emulated device which +exposes a 128-bit, cryptographically random, integer value identifier. +This allows management applications (e.g. libvirt) to notify the guest +operating system when the virtual machine is executed with a different +configuration (e.g. snapshot execution or creation from a template). + +This is specified on the web at: http://go.microsoft.com/fwlink/?LinkId=260709 + +--- + +The vmgenid device is a sysbus device with the ACPI ID "QEMU_Gen_Counter_V1". + +The device has one properties, which can be set using the command line +argument or the QMP interface: + guid - sets the value of the GUID +For example: +QEMU -device vmgenid,guid="324e6eaf-d1d1-4bf6-bf41-b9bb6c91fb87" + +Or to change guid in runtime use: + set-vm-generation-id guid="124e6eaf-d1d1-4bf6-bf41-b9bb6c91fb87" + +According to the specification, any change to the GUID executes an +ACPI notification. The vmgenid device triggers the \_GPE._E00 handler +which executes the ACPI Notify operation. + +Although not specified in Microsoft's document, it is assumed that the +device is expected to use the little-endian system. -- 2.7.4
