Bug 1385264

PowerShell check
PS C:\> (Get-CimInstance Win32_Processor).SecondLevelAddressTranslationExtensions
True
PS C:\> (Get-CimInstance Win32_Processor).VirtualizationFirmwareEnabled
False
PS C:\> (Get-CimInstance Win32_Processor).VMMonitorModeExtensions
True
PS C:\> (Get-CimInstance Win32_OperatingSystem).DataExecutionPrevention_Available
True


WMIC check
C:\>wmic cpu get SecondLevelAddressTranslationExtensions
SecondLevelAddressTranslationExtensions
TRUE
C:\>wmic cpu get VirtualizationFirmwareEnabled
VirtualizationFirmwareEnabled
FALSE
C:\>wmic cpu get VMMonitorModeExtensions
VMMonitorModeExtensions
TRUE
C:\>wmic os get DataExecutionPrevention_Available
DataExecutionPrevention_Available
TRUE

Hi, please provide domain XML of the windows guest, I've tested it and it works so I guess that your XML doesn't enable the correct cpu feature for windows guest.

I have try to use the fedora-virt-preview and kernel-vanilla-stable repo and now it work with these packages (just add the repo and upgrade, no need to change the guest xml)

kernel-4.8.1-1.vanilla.knurd.1.fc24.x86_64
libvirt-2.2.0-1.fc24.x86_64
qemu-kvm-2:2.7.0-3.fc24.x86_64
qemu-system-x86-2:2.7.0-3.fc24.x86_64

It seem to soon to tell.
So the qemu 2.7 packages enable Windows 10 / Server to install Hyper-V, newer kernel or libvirt is not needed.

But Hyper-V still not working correctly. When add this tag <feature policy='disable' name='hypervisor'/>, Hyper-V cannot start VM with error: "Virtual Machine could not be started because the hypervisor is not running"

Without this tag, there is this error "Failed to start the virtual machine because one of the Hyper-V components is not running." and in Device Manager, this component "Microsoft Hyper-V Virtual Machine Bus Provider" report "Windows cannot initialise the device driver for this hardware. (Code 37)"

himasterchief is right. This a bug and it's not resolved.

PS C:\Users\Administrator> (Get-CimInstance Win32_Processor).VirtualizationFirmwareEnabled
True
True

I checked and these features are all enabled as well:
SecondLevelAddressTranslationExtensions - True
VMMonitorModeExtensions - True
DataExecutionPrevention_Available - True

I have also verified with cpuid on the server 2016 at L1 that the vt-x extensions are visible.

But when i try to start a VM on the L1 win2k16 I'm still getting:
"Failed to start the virtual machine blah because one of the Hyper-V components is not running."
WHen i click on details it says the virtual machine management service failed to start the vm for the same reason.

I'm running f25, but i read elsewhere that seabios 1.10 was required for this to work, so i installed seabios-bin.noarch 1.10.1-2.fc26 from rawhide & still no luck.

Qemu is:
qemu-2.7.1-2.fc25.x86_64


My first response would be to say it's microsoft's fault, but it is reported to work at:
https://ladipro.wordpress.com/2017/02/24/running-hyperv-in-kvm-guest/

I have followed all the steps that guy did with 2 exceptions - 
1) I'm running centos 7 guest not win xp
2) i edited my server2016 vm xml config to have

  <cpu mode='host-passthrough'>
  <feature policy='require' name='vmx'/>
  </cpu>

But when started from virt-manager my qemu command line still does not have +vmx on it, which he suggested wass necessary. 

But at this point it looks like vmx is enabled in the server2k16 guest - the host-passthrough should guarantee it is there, and i've had no problems with nested ESXi hosts creating their own L2 VMs, nor with nested RHEV/Ovirt hosts creating their own VMs, with my current configuration

So starting the VM manually with +vmx is my final resort, and I don't expect it will make any difference.

There's definitely something wrong here, and it's probably microsoft's fault, as ESXi and RHEV/Ovirt are fine but if we could defeat Redmond in this battle and get this working that would be awesome...

Even with all th nested virtualisation features i can find, enabled, the error i'm seeing in event viewer is:

Hypervisor launch failed; Processor does not support the minimum features required to run the hypervisor (MSR index 0x48B, allowed bits 0x2600000000, required bits 0x1000FB00000000).

It seem we need qemu 2.7 and kernel 4.10 to make Hyper-V on QEMU/KVM work. You may want to check this, I have not test this yet
https://ladipro.wordpress.com/2017/02/24/running-hyperv-in-kvm-guest/

Aah balls. I'm running fedora 25 i assumed that if someone else had this working my kernel would be new enough, but:

uname -a
Linux blah 4.9.10-200.fc25.x86_64 #1 SMP Wed Feb 15 23:28:59 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

Unbelievable. Why is it that everything you try to do on linux seems to be on the bleeding edge of impossibility.

Anyway thanks for the top himasterchef I'm installing kernel 4.11 from fedora rawhide now, fingers crossed that will fix this!

Bah! The rawhide kernel-4.11.0-0.rc1.git0.1.fc27.x86_64 is no good! The server 2016 VM pegs its CPUs and doesn't stop!

The only 4.10 kernel available for fedora that i can find is at the good jforbes kernel stabilisation repo:

https://copr.fedorainfracloud.org/coprs/jforbes/kernel-stabilization/repo/fedora-25/jforbes-kernel-stabilization-fedora-25.repo

So, fingers Xed for 4.10.1-1.fc25...

Hmm... Ok well, a little progress. No error saying hyper-v components not running this time.

But now it fails with:
"vm blah failed to change state" so there's still a problem.

Doh! I just tried to launch the vm a second time and now it is back to saying one of the hyper-v components is not running.

But there is still nothing in the event log about processor not supporting hyper-v. So that is at least some improvement.

Looks like this is a bit closer to working now, in 4.10.1-1, but still no donut.

I just have sometime to test with kernel 4.10 and it seems working. I have not try to install OS yet, just try to boot VM, work with both gen. I am using kernel from Kernel vanilla repositories.

I only need <cpu mode='host-passthrough'>, not <feature policy='require' name='vmx'/>. I think host-passthrough already pass the vmx flag.

fc24
kernel-4.10.1-1.vanilla.knurd.1.fc24.x86_64    @kernel-vanilla-stable
qemu-kvm-2:2.7.0-8.fc24.x86_64                 @fedora-virt-preview
libvirt-2.2.0-2.fc24.x86_64                    @fedora-virt-preview

I'll have to have another look. I got my wires crossed a bit earlier, when trying the 4.10 kernel from jforbes repo - it turns out i was still getting events from hyper-v about components not running, i just didn't see them at the top level in event viewer i had to drill down into events specifically from hyper-v or look on the server manager page for hyper-v (which is where i saw them originally, but forgot to look there later). 

Another problem i have is that the 4.10 kernel for fedora 25 which i got from jforbes is not stable at all for qemu my VMs don't boot most of the time, just like the 4.11 that i tried. I get pegged cpus, bootup hangs, and reboots with thread exceptions, and kernel module traces on my host console.

Not sure if the 4.10 kernel you're using, from kernel-vanilla-stable is available for f25 but if it is i'll give it a go.