id = 2063
title = "Poor performance with -accel whpx on Server 2022 host, windows 10 guest - missing CPUID hypervisor ident data?"
state = "opened"
created_at = "2023-12-30T23:23:02.500Z"
closed_at = "n/a"
labels = ["accel: WHPX", "target: i386"]
url = "https://gitlab.com/qemu-project/qemu/-/issues/2063"
host-os = "Windows Server 2022"
host-arch = "x86-64"
qemu-version = "QEMU emulator version 8.2.0 (v8.2.0-12045-g3d58f9b5c5)"
guest-os = "Windows 10"
guest-arch = "x86-64"
description = """**Performance of Windows 10 x64 QEMU virtual machine is essentially unusable, compared to same image running under Hyper-V on the same host system.**

It appears the VM is not being provided the Hyper-V enlightenment hints while running under QEMU.  The hv-XXX cpu options do not appear applicable to -accel WHPX.

Below are dumps of the 0x40000000 cpuid values on the host, QEMU guest, and Hyper-V guest (exact same .VHD file used, nested virtualization not enabled for this VM).

host:
- 0x40000000 eax=4000000c ebx=7263694d ecx=666f736f edx=76482074
- 0x40000001 eax=31237648 ebx=0 ecx=0 edx=0
- 0x40000002 eax=4f7c ebx=a0000 ecx=2 edx=85d
- 0x40000003 eax=bfff ebx=2bb9ff ecx=22 edx=71fffbf6
- 0x40000004 eax=50d1c ebx=fff ecx=0 edx=0
- 0x40000005 eax=400 ebx=400 ecx=ba00 edx=0
- 0x40000006 eax=1e00be ebx=0 ecx=0 edx=0
- 0x40000007 eax=80000007 ebx=3 ecx=0 edx=0
- 0x40000008 eax=100001 ebx=1 ecx=aaaa edx=0
- 0x40000009 eax=0 ebx=0 ecx=0 edx=0
- 0x4000000a eax=0 ebx=0 ecx=0 edx=0
- 0x4000000b eax=0 ebx=0 ecx=0 edx=0
- 0x4000000c eax=0 ebx=0 ecx=0 edx=0

qemu guest with -accel whpx : 
- 0x40000000 eax=40000010 ebx=0 ecx=0 edx=0
- 0x40000001 eax=0 ebx=0 ecx=0 edx=0
- 0x40000002 eax=0 ebx=0 ecx=0 edx=0
- 0x40000003 eax=0 ebx=0 ecx=0 edx=0
- 0x40000004 eax=0 ebx=0 ecx=0 edx=0
- 0x40000005 eax=0 ebx=0 ecx=0 edx=0
- 0x40000006 eax=0 ebx=0 ecx=0 edx=0
- 0x40000007 eax=0 ebx=0 ecx=0 edx=0
- 0x40000008 eax=0 ebx=0 ecx=0 edx=0
- 0x40000009 eax=0 ebx=0 ecx=0 edx=0
- 0x4000000a eax=0 ebx=0 ecx=0 edx=0
- 0x4000000b eax=0 ebx=0 ecx=0 edx=0
- 0x4000000c eax=0 ebx=0 ecx=0 edx=0
- 0x4000000d eax=0 ebx=0 ecx=0 edx=0
- 0x4000000e eax=0 ebx=0 ecx=0 edx=0
- 0x4000000f eax=0 ebx=0 ecx=0 edx=0
- 0x40000010 eax=225519 ebx=30d40 ecx=0 edx=0

hyperv guest VM: (nested virtualization not enabled)
- 0x40000000 eax=4000000b ebx=7263694d ecx=666f736f edx=76482074
- 0x40000001 eax=31237648 ebx=0 ecx=0 edx=0
- 0x40000002 eax=4f7c ebx=a0000 ecx=2 edx=85d
- 0x40000003 eax=ae7f ebx=388030 ecx=22 edx=e0bed7b2
- 0x40000004 eax=40c2c ebx=fff ecx=0 edx=0
- 0x40000005 eax=f0 ebx=400 ecx=ba00 edx=0
- 0x40000006 eax=e ebx=0 ecx=0 edx=0
- 0x40000007 eax=0 ebx=0 ecx=0 edx=0
- 0x40000008 eax=0 ebx=0 ecx=0 edx=0
- 0x40000009 eax=0 ebx=0 ecx=0 edx=0
- 0x4000000a eax=0 ebx=0 ecx=0 edx=0
- 0x4000000b eax=0 ebx=0 ecx=0 edx=0"""
reproduce = "n/a"
additional = "n/a"