Re: [Qemu-devel] [PATCH V15 1/5] docs: vm generation id device's description

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Apr 27, 2015 at 02:19:47PM +0300, Gal Hammer wrote:
> Signed-off-by: Gal Hammer <ghammer@redhat.com>
> ---
>  docs/specs/vmgenid.txt | 35 +++++++++++++++++++++++++++++++++++
>  1 file changed, 35 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..86ce6ab
> --- /dev/null
> +++ b/docs/specs/vmgenid.txt
> @@ -0,0 +1,35 @@
> +VIRTUAL MACHINE GENERATION ID
> +=============================
> +
> +Copyright (C) 2014 Red Hat, Inc.

It's 2015, isn't it?

> +
> +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.

The value is up to user, let's not claim it's cryptographically random.

> +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".

No one is expected to locate it using that ID, right?

> +
> +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: 0xfedf0000-0xfedf000f to store
> +the GUID's buffer.
> +
> +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.
> -- 
> 2.1.0