Signed-off-by: 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..656d598 --- /dev/null +++ b/docs/specs/vmgenid.txt @@ -0,0 +1,38 @@ +VIRTUAL MACHINE GENERATION ID +============================= + +Copyright (C) 2014 Red Hat, 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 following ACPI ID: +"QEMU0002". + +The device adds a "vmgenid.uuid" property, which can be modified using +the -global command line argument or the QMP interface. + +The device uses a fixed memory resource: 0xfedf0000-0xfedf0003. The +guest is expected to write the physical address of the GUID's buffer +to that memory resource. This allows the device to modify the GUID if +requested by the management application. Current device's implementation +supports a 32-bit address. + +According to the specification, any change to the GUID executes an +ACPI notification. The vmgenid device triggers the GPE._E00 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. -- 1.9.3
