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[67.207.112.138]) by smtp.gmail.com with ESMTPSA id p20sm7773759itc.8.2016.12.19.14.46.38 (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 19 Dec 2016 14:46:38 -0800 (PST) From: ben@skyportsystems.com To: qemu-devel@nongnu.org Date: Mon, 19 Dec 2016 14:46:30 -0800 Message-Id: X-Mailer: git-send-email 2.10.1 (Apple Git-78) In-Reply-To: References: In-Reply-To: References: X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 2607:f8b0:4001:c0b::234 Subject: [Qemu-devel] [PATCH 1/5] docs: vm generation id device's description X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Gal Hammer , Ben Warren Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" From: Ben Warren Signed-off-by: Ben Warren Cc: Gal Hammer --- docs/specs/vmgenid.txt | 39 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 39 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..94277a9 --- /dev/null +++ b/docs/specs/vmgenid.txt @@ -0,0 +1,39 @@ +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 two properties, which can be set using the command line +argument or the QMP interface: + guid - sets the value of the GUID + changed - signals that the value has changed since the last invocation +For example: +QEMU -device vmgenid,changed=true,guid="324e6eaf-d1d1-4bf6-bf41-b9bb6c91fb87" + +Or to change guid in runtime use: + set-vm-generation-id changed=true 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.