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[V10,1/3] docs: vm generation id device's description

Message ID 1418546511-13063-2-git-send-email-ghammer@redhat.com
State New
Headers show

Commit Message

Gal Hammer Dec. 14, 2014, 8:41 a.m. UTC 
Signed-off-by: Gal Hammer <ghammer@redhat.com>

---
 docs/specs/vmgenid.txt | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)
 create mode 100644 docs/specs/vmgenid.txt
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Patch

diff --git a/docs/specs/vmgenid.txt b/docs/specs/vmgenid.txt
new file mode 100644
index 0000000..656d598
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+++ b/docs/specs/vmgenid.txt
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+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.