[vfio-users] Cloning qcwo2 image to native install and boot it with qemu?

Arjen arjenvanweelden at gmail.com
Sun Apr 17 14:04:20 UTC 2016

On 04/17/2016 03:08 PM, thibaut noah wrote:
> Hi guys, so i did some thinking and a bit of reading and it seems some
> people are currently running native windows install with qemu.
> Since it would be the best of both worlds, allowing me to dual boot
> windows for native benchmarks and all i'm thinking about making the leap.
> Though i could use some advice if people here have done that already.
> First i will start with my current situation, since i have a qcwo2 image
> on the disk i want to install windows on, i would first need to make a
> snapshot or a copy of said image on another disk, that part seems easy
> enough.
> Then comes the tricky part, i would need to unmount my ssd, format it
> with proper partitionning? and then cloning directly from my virtualize
> windows my install to the ssd using most likely acronis.
> Anyone attempted this before? The cloning part i mean, it seems logic to
> me that it would work but i really have no idea.
> I could just reinstall everything except i have a crappy connection
> (250ko/s for 6 people) and it took me weeks to get every soft and games
> i needed.
> Also on the performance side with qemu i don't know what is the proper
> way to partition the ssd before cloning windows, i'm not even sure i
> actually need to partition anything, maybe the cloning software can do
> it for me.
> After that, and supposing everything works i assume i just have to pass
> the disk to qemu without mounting it.
> Dual boot might be tricky since i'll need to update mbr and since i use
> grub that would require some digging.
> Anyway, if any of you folks have some knowledge on that please feel free
> to share it, that seems like a nice way to get people switching from
> dual boot to vfio :)
I did something similar, but much simpler with FreeDOS. A second HDD has 
a MBR that boots the first FAT partition (when selected in BIOS). I 
installed FreeDOS by running it in a VM to which I passed the entire 
/dev/sdb HDD and installation ISO. FreeDOS just ignores all other 
(Linux) partitions and works the same whether I boot it bare-metal (for 
firmware updates of hardware) or within qemu VM.

Windows partitions might be more complex nowadays and it can be 
dangerous to pass entire /dev/sdb to a VM while other VMs use /dev/sdb2 
etc. I also worry about Windows detecting different hardware and 
(re)installing drivers, which might require a reboot after switching 
between bare-metal and VM. Also the Windows license check might complain 
about the changing hardware.

kind regards, Arjen

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