PVE freezes when processor type is set to "host"

[omyno]

Because it took me way longer than I hoped for, I would like to share a little detail about the necessity of setting a compatible CPU type for the guest machine.

Environment:

• Hardware: Intel Alder Lake-S GT1 [UHD Graphics 730]
• Hypervisor: Proxmox 8.0.4
• VM:

VM config

root@proxmox:/etc/pve/qemu-server# cat 100.conf 
bios: ovmf
hostpci0: 0000:00:02.1,x-vga=1
machine: q35
vga: none
cpu: host

dmesg |grep i915

[    0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-6.2.16-15-pve root=/dev/mapper/pve-root ro quiet intel_iommu=on i915.enable_guc=3 i915.max_vfs=7 pcie_acs_override=downstream,multifunction
[    0.050714] Kernel command line: BOOT_IMAGE=/boot/vmlinuz-6.2.16-15-pve root=/dev/mapper/pve-root ro quiet intel_iommu=on i915.enable_guc=3 i915.max_vfs=7 pcie_acs_override=downstream,multifunction
[    5.384873] i915: module verification failed: signature and/or required key missing - tainting kernel
[    5.542743] i915 0000:00:02.0: Running in SR-IOV PF mode
[    5.543435] i915 0000:00:02.0: [drm] VT-d active for gfx access
[    5.543457] i915 0000:00:02.0: vgaarb: deactivate vga console
[    5.543497] i915 0000:00:02.0: [drm] Using Transparent Hugepages
[    5.544103] i915 0000:00:02.0: vgaarb: changed VGA decodes: olddecodes=io+mem,decodes=io+mem:owns=io+mem
[    5.544811] mei_hdcp 0000:00:16.0-b638ab7e-94e2-4ea2-a552-d1c54b627f04: bound 0000:00:02.0 (ops i915_hdcp_component_ops [i915])
[    5.552940] i915 0000:00:02.0: [drm] Finished loading DMC firmware i915/adls_dmc_ver2_01.bin (v2.1)
[    5.556704] i915 0000:00:02.0: [drm] GT0: GuC firmware i915/tgl_guc_70.bin version 70.5.1
[    5.556707] i915 0000:00:02.0: [drm] GT0: HuC firmware i915/tgl_huc.bin version 7.9.3
[    5.558979] i915 0000:00:02.0: [drm] GT0: HuC: authenticated for all workloads!
[    5.559321] i915 0000:00:02.0: [drm] GT0: GUC: submission enabled
[    5.559322] i915 0000:00:02.0: [drm] GT0: GUC: SLPC enabled
[    5.559705] i915 0000:00:02.0: [drm] GuC RC: enabled
[    5.561921] mei_pxp 0000:00:16.0-fbf6fcf1-96cf-4e2e-a6a6-1bab8cbe36b1: bound 0000:00:02.0 (ops i915_pxp_tee_component_ops [i915])
[    5.562761] i915 0000:00:02.0: [drm] Protected Xe Path (PXP) protected content support initialized
[    5.566281] [drm] Initialized i915 1.6.0 20201103 for 0000:00:02.0 on minor 0
[    5.568597] snd_hda_intel 0000:00:1f.3: bound 0000:00:02.0 (ops i915_audio_component_bind_ops [i915])
[    5.568718] i915 0000:00:02.0: 7 VFs could be associated with this PF
[    5.569152] i915 0000:00:02.0: [drm] Cannot find any crtc or sizes
[    5.569778] i915 0000:00:02.0: [drm] Cannot find any crtc or sizes
[   52.553145] i915 0000:00:02.0: vgaarb: changed VGA decodes: olddecodes=io+mem,decodes=none:owns=io+mem
[   52.553208] i915 0000:00:02.1: enabling device (0000 -> 0002)
[   52.553221] i915 0000:00:02.1: Running in SR-IOV VF mode
[   52.553553] i915 0000:00:02.1: [drm] GT0: GUC: interface version 0.1.0.0
[   52.555220] i915 0000:00:02.1: [drm] VT-d active for gfx access
[   52.555235] i915 0000:00:02.1: [drm] Using Transparent Hugepages
[   52.555620] i915 0000:00:02.1: [drm] GT0: GUC: interface version 0.1.0.0
[   52.555930] i915 0000:00:02.1: GuC firmware PRELOADED version 1.0 submission:SR-IOV VF
[   52.555932] i915 0000:00:02.1: HuC firmware PRELOADED
[   52.557846] i915 0000:00:02.1: [drm] Protected Xe Path (PXP) protected content support initialized
[   52.557850] i915 0000:00:02.1: [drm] PMU not supported for this GPU.
[   52.557897] [drm] Initialized i915 1.6.0 20201103 for 0000:00:02.1 on minor 1
[   52.558190] i915 0000:00:02.0: vgaarb: changed VGA decodes: olddecodes=none,decodes=none:owns=io+mem
[   52.558192] i915 0000:00:02.1: vgaarb: changed VGA decodes: olddecodes=io+mem,decodes=none:owns=none
[   52.558259] i915 0000:00:02.2: enabling device (0000 -> 0002)
[   52.558269] i915 0000:00:02.2: Running in SR-IOV VF mode
[   52.558594] i915 0000:00:02.2: [drm] GT0: GUC: interface version 0.1.0.0
[   52.559162] i915 0000:00:02.2: [drm] VT-d active for gfx access
[   52.559174] i915 0000:00:02.2: [drm] Using Transparent Hugepages
[   52.559528] i915 0000:00:02.2: [drm] GT0: GUC: interface version 0.1.0.0
[   52.559848] i915 0000:00:02.2: GuC firmware PRELOADED version 1.0 submission:SR-IOV VF
[   52.559849] i915 0000:00:02.2: HuC firmware PRELOADED
[   52.561659] i915 0000:00:02.2: [drm] Protected Xe Path (PXP) protected content support initialized
[   52.561661] i915 0000:00:02.2: [drm] PMU not supported for this GPU.

When

1. i915-sriov-dkms is installed on the guest system (Ubuntu 22.04),
2. and cpu type of guest VM is "host",
3. and the guest system is being started,
4. then the host freezes almost immediately. I can still type a few characters within the SSH session with a delay of 20 seconds.

When switching the CPU type to x86-64-v2-AES, everything works perfectly.