I run Debian on my laptop (obviously); but occasionally, for $DAYJOB, I have some work to do on Windows. In order to do so, I have had a Windows 10 VM in my libvirt configuration that I can use.

A while ago, Microsoft issued Windows 11. I recently found out that all the components for running Windows 11 inside a libvirt VM are available, and so I set out to upgrade my VM from Windows 10 to Windows 11. This wasn't as easy as I thought, so here's a bit of a writeup of all the things I ran against, and how I fixed them.

Windows 11 has a number of hardware requirements that aren't necessary for Windows 10. There are a number of them, but the most important three are:

  • Secure Boot is required (Windows 10 would still boot on a machine without Secure Boot, although buying hardware without at least support for that hasn't been possible for several years now)
  • A v2.0 TPM module (Windows 10 didn't need any TPM)
  • A modern enough processor.

So let's see about all three.

A modern enough processor

If your processor isn't modern enough to run Windows 11, then you can probably forget about it (unless you want to use qemu JIT compilation -- I dunno, probably not going to work, and also not worth it if it were). If it is, all you need is the "host-passthrough" setting in libvirt, which I've been using for a long time now. Since my laptop is less than two months old, that's not a problem for me.

A TPM 2.0 module

My Windows 10 VM did not have a TPM configured, because it wasn't needed. Luckily, a quick web search told me that enabling that is not hard. All you need to do is:

  • Install the swtpm and swtpm-tools packages

  • Adding the TPM module, by adding the following XML snippet to your VM configuration:

    <devices>
  <tpm model='tpm-tis'>
    <backend type='emulator' version='2.0'/>
  </tpm>
</devices>

    Alternatively, if you prefer the graphical interface, click on the "Add hardware" button in the VM properties, choose the TPM, set it to Emulated, model TIS, and set its version to 2.0.

You're done!

Well, with this part, anyway. Read on.

Secure boot

Here is where it gets interesting.

My Windows 10 VM was old enough that it was configured for the older i440fx chipset. This one is limited to PCI and IDE, unlike the more modern q35 chipset (which supports PCIe and SATA, and does not support IDE nor SATA in IDE mode).

There is a UEFI/Secure Boot-capable BIOS for qemu, but it apparently requires the q35 chipset,

Fun fact (which I found out the hard way): Windows stores where its boot partition is somewhere. If you change the hard drive controller from an IDE one to a SATA one, you will get a BSOD at startup. In order to fix that, you need a recovery drive. To create the virtual USB disk, go to the VM properties, click "Add hardware", choose "Storage", choose the USB bus, and then under "Advanced options", select the "Removable" option, so it shows up as a USB stick in the VM. Note: this takes a while to do (took about an hour on my system), and your virtual USB drive needs to be 16G or larger (I used the libvirt default of 20G).

There is no possibility, using the buttons in the virt-manager GUI, to convert the machine from i440fx to q35. However, that doesn't mean it's not possible to do so. I found that the easiest way is to use the direct XML editing capabilities in the virt-manager interface; if you edit the XML in an editor it will produce error messages if something doesn't look right and tell you to go and fix it, whereas the virt-manager GUI will actually fix things itself in some cases (and will produce helpful error messages if not).

What I did was:

  • Take backups of everything. No, really. If you fuck up, you'll have to start from scratch. I'm not responsible if you do.
  • Go to the Edit->Preferences option in the VM manager, then on the "General" tab, choose "Enable XML editing"
  • Open the Windows VM properties, and in the "Overview" section, go to the "XML" tab.
  • Change the value of the machine attribute of the domain.os.type element, so that it says pc-q35-7.0.
  • Search for the domain.devices.controller element that has pci in its type attribute and pci-root in its model one, and set the model attribute to pcie-root instead.
  • Find all domain.devices.disk.target elements, setting their dev=hdX to dev=sdX, and bus="ide" to bus="sata"
  • Find the USB controller (domain.devices.controller with type="usb", and set its model to qemu-xhci. You may also want to add ports="15" if you didn't have that yet.

  • Perhaps also add a few PCIe root ports:

    <controller type="pci" index="1" model="pcie-root-port"/>
<controller type="pci" index="2" model="pcie-root-port"/>
<controller type="pci" index="3" model="pcie-root-port"/>

I figured out most of this by starting the process for creating a new VM, on the last page of the wizard that pops up selecting the "Modify configuration before installation" option, going to the "XML" tab on the "Overview" section of the new window that shows up, and then comparing that against what my current VM had.

Also, it took me a while to get this right, so I might have forgotten something. If virt-manager gives you an error when you hit the Apply button, compare notes against the VM that you're in the process of creating, and copy/paste things from there to the old VM to make the errors go away. As long as you don't remove configuration that is critical for things to start, this shouldn't break matters permanently (but hey, use your backups if you do break -- you have backups, right?)

OK, cool, so now we have a Windows VM that is... unable to boot. Remember what I said about Windows storing where the controller is? Yeah, there you go. Boot from the virtual USB disk that you created above, and select the "Fix the boot" option in the menu. That will fix it.

Ha ha, only kidding. Of course it doesn't.

I honestly can't tell you everything that I fiddled with, but I think the bit that eventually fixed it was where I chose "safe mode", which caused the system to do a hickup, a regular reboot, and then suddenly everything was working again. Meh.

Don't throw the virtual USB disk away yet, you'll still need it.

Anyway, once you have it booting again, you will now have a machine that theoretically supports Secure Boot, but you're still running off an MBR partition. I found a procedure on how to convert things from MBR to GPT that was written almost 10 years ago, but surprisingly it still works, except for the bit where the procedure suggests you use diskmgmt.msc (for one thing, that was renamed; and for another, it can't touch the partition table of the system disk either).

The last step in that procedure says to restart your computer!, which is fine, except at this point you obviously need to switch over to the TianoCore firmware, otherwise you're trying to read a UEFI boot configuration on a system that only supports MBR booting, which obviously won't work. In order to do that, you need to add a loader element to the domain.os element of your libvirt configuration:

<loader readonly="yes" type="pflash">/usr/share/OVMF/OVMF_CODE_4M.ms.fd</loader>

When you do this, you'll note that virt-manager automatically adds an nvram element. That's fine, let it.

I figured this out by looking at the documentation for enabling Secure Boot in a VM on the Debian wiki, and using the same trick as for how to switch chipsets that I explained above.

Okay, yay, so now secure boot is enabled, and we can install Windows 11! All good? Well, almost.

I found that once I enabled secure boot, my display reverted to a 1024x768 screen. This turned out to be because I was using older unsigned drivers, and since we're using Secure Boot, that's no longer allowed, which means Windows reverts to the default VGA driver, and that only supports the 1024x768 resolution. Yeah, I know. The solution is to download the virtio-win ISO from one of the links in the virtio-win github project, connecting it to the VM, going to Device manager, selecting the display controller, clicking on the "Update driver" button, telling the system that you have the driver on your computer, browsing to the CD-ROM drive, clicking the "include subdirectories" option, and then tell Windows to do its thing. While there, it might be good to do the same thing for unrecognized devices in the device manager, if any.

So, all I have to do next is to get used to the completely different user interface of Windows 11. Sigh.

Oh, and to rename the "w10" VM to "w11", or some such. Maybe.