I was doing a bit of investigation around how different hypervisors
handle the VM Generation ID feature. QEMU's behaviour seems quite
strange, I wonder if this is a bug or expected?
(1) I booted a Windows 2016 VM with:
qemu-system-x86_64 -M pc,accel=kvm -m 2G -hda w2k16-mincore.img \
-device vmgenid,guid=01020304-0506-0708-090a-0b0c0d0e0f00,id=vmgenid0
(2) Inside the guest I used the VMGENID.EXE program from:
https://bugzilla.redhat.com/show_bug.cgi?id=1598350#c3
https://docs.microsoft.com/en-gb/windows/desktop/HyperV_v2/virtual-machine-generation-identifier
Note this is self-compiled using mingw64-g++ (not using Visual Studio
which I don't have available), but I don't believe that could have
caused the problem.
(3) The program prints:
VmCounterValue: 708050601020304:f0e0d0c0b0a09
To make it easier to see, this is the same number but zero-extended:
VmCounterValue: 07 08 05 06 01 02 03 04 : 00 0f 0e 0d 0c 0b 0a 09
\________ LOW ________/ \_______ HIGH _______/
WORD WORD
As you can see it looks like there is no clear relationship between
the order of the bytes in the guid= parameter and the order that they
are seen by Windows.
BTW if you want to try to reproduce this you will need to use
Windows 2012 R2 or above.
Rich.
--
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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