Poor user experience with Windows Server 2025 on Proxmox

Last edited:
  • Like
Reactions: Johannes S
Are there any news here?
I have exactly the same issue as the OP describes: laggy UI elements like explorer and context menu with my Server 2025 VM's, while the Server 2022 are unaffected.

I checked out all the suggestions given here and in this thread - none has helped so far.

In contrast to the OP I have more modern hardware, in this case:
Code: 
CPU(s) 48 x AMD EPYC 9254 24-Core Processor (1 Socket)
Kernel Version Linux 7.0.14-15-pve (2026-08-26T14:21Z)
Boot Mode EFI
Manager Version pve-manager/9.2.11/f6997e698c7933ea
 
niteshadow said:
I am assuming this is a clean Windows Server 2025, with just virtio-win-guest-tools installed.
Can you post your VM configuration ?
Click to expand...

No, it is not clean generally. The image has some hardening settings applied.
Regarding running software, it is clean. No third party software is running on this test machine.

You are right, I should probably get my hands on a clean Server 2025 image and compare.
I would not have guessed that the hardening settings would cause an issue like that.

EDIT: I remembered, that there is another proxmox here on older machine. I will deploy this vm onto that machine and compare and report here.

Code: 
 ...:~# qm config 405
bios: ovmf
boot: order=scsi0
cores: 6
cpu: host
efidisk0: vm_nvme:vm-405-disk-0,efitype=4m,ms-cert=2023w,pre-enrolled-keys=1,size=1M
machine: q35
memory: 16000
name: Admin-Server
net0: virtio=BC:24:11:CC:D0:BA,bridge=vmbr0
numa: 0
scsi0: vm_nvme:vm-405-disk-1,iothread=1,size=250G
scsi1: vm_nvme:vm-405-disk-2,iothread=1,size=100G
scsihw: virtio-scsi-single
smbios1: uuid=69b5aa2b-c149-4efa-a0b6-df227e2296c5
sockets: 1
vmgenid: 7bf94186-cf30-41b2-af34-773e444ca82c
 
Last edited:
  • Like
Reactions: Johannes S
Looks like you have not enabled the QEMU Guest Agent, which I feel is important.You should also install all the guest tools.
Otherwise seems OK (but I personally don't use cpu "host" as I value portability). My recent Server 2025 conf:

Code: 
agent: 1
bios: ovmf
boot: order=scsi0;ide2;net0
cores: 6
cpu: x86-64-v3
efidisk0: data:vm-740-disk-0,efitype=4m,ms-cert=2023k,pre-enrolled-keys=1,size=1M
ide2: none,media=cdrom
machine: pc-q35-11.0
memory: 16384
meta: creation-qemu=11.0.0,ctime=1783628049
name: pro2025
net0: virtio=BC:24:11:05:EC:6C,bridge=vmbr1,firewall=1,tag=20
numa: 1
onboot: 1
ostype: win11
scsi0: data:vm-740-disk-1,discard=on,iothread=1,size=160G
scsihw: virtio-scsi-single
smbios1: uuid=6f5b6dc4-9956-442d-968c-67ec693f63a6
sockets: 2
tpmstate0: data:vm-740-disk-2,size=4M,version=v2.0
vmgenid: f1193023-16fd-4996-a06c-c28084bc3159
 
elhannio said:
cpu: host
Click to expand...
there's your problem.

Host exposes the full set of cpu flags to the guest, which means all mitigations applicable to your cpu will apply. in a virtualized environment, mitigations will destroy guest performance- Windows most of all.

Additionally, Windows 11/2025 introduced hard feature dependencies for cpu support. Older CPUs (pre Haswell) do not have those features, which is why the official installer would not let you install on such hardware.

Depending on your use case, you have three choices:
1. use x86-64-V3 (or better) cpu type. this will mask your cpuid to prevent windows from activating mitigation code. its also possible to granularly control cpu features with a customized cpu type. the downside is that vulnerability mitigations would not be enabled, making this inadvisable for production use.
2. Upgrade your host hardware.
3. stick to older Windows kernels (windows10/2022)
(and obligatory 4) dont use windows.
 
  • Like
Reactions: Johannes S
You must log in or register to reply here.
Top Bottom
Back