id = 1031
title = "Intel 12th Gen CPU not working with QEMU Hyper-V nested virtualization"
state = "opened"
created_at = "2022-05-19T13:42:11.330Z"
closed_at = "n/a"
labels = ["accel: WHPX", "target: i386"]
url = "https://gitlab.com/qemu-project/qemu/-/issues/1031"
host-os = "Manjaro"
host-arch = "x86_64"
qemu-version = "QEMU emulator version 7.0.0"
guest-os = "Windows 10"
guest-arch = "x86_64"
description = """When booting with Hyper-V + host-passthrough it gets stuck at tianocore, does not change until I reboot which then loops into windows diagnostics which leads nowhere. Done using Windows 10, tried using newest windows version and 1909.

Specs: Manjaro Gnome 5.15 LTS, i5-12600k, z690 gigabyte aorus elite ddr4, rtx 3070ti.

I’ve spent days trying to figure out what was messing with it and it turned out I could boot when messing with my CPU topology, for some reason my 12th gen + Hyper-V + host-passthrough only works with sockets. Cores and threads above 1 causes boot problems, apart from disabling vme which boots, but the hypervisor does not load.

This fails (normal host-passthrough):
```
  <cpu mode="host-passthrough" check="none" migratable="on">
    <topology sockets="1" dies="1" cores="6" threads="2"/>
  </cpu>
```

This boots (-can only change sockets):
```
  <cpu mode="host-passthrough" check="none" migratable="on">
    <topology sockets="12" dies="1" cores="1" threads="1"/>
  </cpu>
```

This boots (-no hypervisor):
```
<cpu mode="host-passthrough" check="partial" migratable="off">
    <topology sockets="1" dies="1" cores="6" threads="2"/>
    <feature policy="disable" name="vme"/>
  </cpu>
```

No matter what adjustment I do I cannot change the cores or threads or it will result in a boot failure, host-model just does not work once I boot the machine the host model changes to cooperlake.

My current way of bypassing this is I’ve downloaded the QEMU source code, gone through cpu.c and modified the default skylake-client CPU model to match my CPU, then I added in most of my i5-12600k flags manually, this seems to work with a 35-45% performance drop in CPU and in ram. Without Hyper-V enabled and using the normal host-passthrough I get near bare metal performance.

Tried with multiple versions of QEMU, EDK2, and loads of kernel versions (to add to this my i5-12600k gen does not work on kernel version 5.13 and below) even went ahead to try Ubuntu and had the same problem, my other (i7-9700k) PC works fine with Hyper-V. Also disabled my E-cores through bios resulting in the same issue. CPU pinning the P-cores to the guest does not seem to help."""
reproduce = """1. Enable hyper-v in windows features
2. Restart guest
3. Boot failure"""
additional = """Hyper-V host-passthrough XML:
https://pst.klgrth.io/paste/yc5wk"""