Hyper-V on Windows Server 2022 cannot load images converted from OVA to VHDX by qemu-img: Boot failure. Reboot and Select proper Boot device or Insert Boot Media in selected Boot device
Description of problem:
We have reference OVA image: https://storage.googleapis.com/fastnetmon_advanced_vm_images/fastnetmon-ubuntu-22.04-amd64-2.0.360.0.ova and we want to convert it to VMDX format.
Steps to reproduce:
I downloaded reference OVA and converted it to VMDX with three possible options.

With subformat dynamic:
```
qemu-img convert fastnetmon-ubuntu-22.04-amd64-2.0.360.0.ova -O vhdx -o subformat=dynamic fastnetmon-ubuntu-22.04-amd64-2.0.360.0.vhdx
```

And without it:
```
qemu-img convert fastnetmon-ubuntu-22.04-amd64-2.0.360.0.ova -O vhdx fastnetmon-ubuntu-22.04-amd64-2.0.360.0.vhdx
```

And with explicitly setting fixed:
```
qemu-img convert fastnetmon-ubuntu-22.04-amd64-2.0.360.0.ova -O vhdx -o subformat=fixed fastnetmon-ubuntu-22.04-amd64-2.0.360.0.vhdx
```

In all cases I tried loading images using VM of Generation 1 and Generation 2:
```
The application encountered an error while attempting to change the state of
'New Virtual Machine'.

'New Virtual Machine' failed to start.

Microsoft Emulated IDE Controller (Instance ID 83F8638B-8DCA-4152-9EDA-2CA8B33039B4): Failed to Power on with Error 'The requested operation could not be completed due to a virtual disk system limitation. Virtual hard disk files must be uncompressed and unencrypted and must not be sparse..

Failed to open attachment 'C:\Program Files\qemu\fastnetmon_non_dynamic.hdx''. Error: 'The requested operation could not be completed due to a virtual disk system limitation. Virtual hard disk files must be uncompressed and unencrypted and must not be sparse..

Failed to open attachment 'C:\Program Files\qemu\fastnetmon_non_dynamic.vhdx'. Error: 'The requested operation could not be completed due to a virtual disk system limitation. Virtual hard disk files must be uncompressed and unencrypted and must not be sparse.'.
```

I noticed some similarities with https://gitlab.com/qemu-project/qemu/-/issues/136 and applied workaround to fix it:
```
fsutil sparse setflag fastnetmon-ubuntu-22.04-amd64-2.0.360.0.vhdx 0
``` 

It started complaining that file is being used by another app. I waited long enough and then rebooted server. 

After that error changed to:
```
Boot failure. Reboot and Select proper Boot device or Insert Boot Media in selected Boot device_
```

As image:

![Screenshot_from_2024-03-02_21-15-10](/uploads/9e172b941d160d2538cf903c1249e9d8/Screenshot_from_2024-03-02_21-15-10.png)

For Generation 2 error is slightly different:
```
Virtual Machine Boot Summary
1. SCSI Disk
(0,0)
The boot loader did not load an operating system.
2. Network Adapter (00155D01770C)
A boot image was not found.
```

As image: ![Screenshot_from_2024-03-02_21-36-37](/uploads/d3bc3ac142096e0ef6fc25e91c299ebc/Screenshot_from_2024-03-02_21-36-37.png)

I tried doing conversion from VirtualBox with same OVA and it worked just fine:
```
VBoxManage clonehd fastnetmon-ubuntu-22.04-amd64-disk1.vmdk fastnetmon.vhd --format vhd
```

I believe something is wrong with boot records for VMDX images.

Example of converted VHDX with dynamic flag can be found here: https://storage.googleapis.com/fastnetmon_advanced_vm_images/fastnetmon-ubuntu-22.04-amd64-2.0.356.0.vhdx 

By Pavel Odintsov at FastNetMon.com