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Re: [Qemu-devel] Byte ordering of VM Generation ID in Windows VMs

From: Richard W.M. Jones
Subject: Re: [Qemu-devel] Byte ordering of VM Generation ID in Windows VMs
Date: Thu, 5 Jul 2018 17:43:43 +0100
User-agent: Mutt/1.5.21 (2010-09-15)

On Thu, Jul 05, 2018 at 04:20:33PM +0200, Laszlo Ersek wrote:
> QEMU does the right thing. If other hypervisors don't do this -- while
> still taking and displaying the value in UUID / GUID textual format --,
> they are wrong. The VMGENID spec from Microsoft
> <http://go.microsoft.com/fwlink/?LinkId=260709> specifically mentions
> "GUID".

The MSFT spec does mention GUID, but it seems to me that it's only
using GUID as an incidental example -- ie. that you might use the VM
Generation ID to generate a GUID.  Outside that example it
consistently refers to the VM Gen ID as a 128-bit integer.  It also
says that it could be used as a "high entropy random data source",
which is not in fact true if it's a UUID.

It has to be said that after reading the spec again [the MSFT spec,
not qemu's spec] and what other hypervisors are doing, I'm not sure
qemu is doing the right thing here.


Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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