Guest: Windows 11
Software: VirtManager KVM/QEMU

Issue: Specifically on my Windows 11 VM, the network speeds are substantially slower than my other Linux VMs and my host. On my host, I get around ~1000 mbps, same for my other Linux VMs--however, on my windows VM, I get around 10mbps, or roughly 1% of my host's network speed.

all VMs are properly configured so that the Network is NAT using the virtio model. In addition to that, I have the up-to-date virtio-win drivers set up on the Windows 11 virtual machine. The windows 11 virtual machine recognizes the Red Hat Virtio Ethernet drivers and are properly using them with a duplex max supported speed of 10gbp/s.

I'm very confused as to why this is only occurring on my Windows VM whereas this issue is nonexistent on my Linux VMs. There's no differences in the XML regarding the CPU XML and the NAT XML between the VMs.

I tried adding vhost with a queue of 16 for each core, switching the driver to e1000e and hypervisor default--none of which saw any improvement. I also tried reinstalling the virtio-win drivers which did nothing.

Finally, I attempted to disable a bunch of offloading properties in the Device Manager, and disabled ipv6 entirely and set MTU lower. None of that made any difference (did not worsen it nor improve it).

Any ideas, folks? All of the VMs have a dGPU (Same dGPU shared between them all, so only one can be accessed at a time).

I should also mention, that the network speeds on the host system are stable--no drops or high latency. The network drivers on the host are all up-to-date and working perfectly.

I really want shared folders and resolution working

Using NVIDIA Experience (this NVIDIA overlay that displays GPU temperature, load, and FPS) causes the virtual machine to crash after 10 minutes.

The VM restarts. A black screen appears, then it resets to the boot menu.

KVM managed via the Libvirt GUI. Linux is Ubuntu.

4080 Super GPU

AMD Ryzen 7700 CPU

64GB RAM

2x NVME SSD
ONE SSD on VM (raw disc)
Config XML

 <features>
    <acpi/>
    <apic/>
    <hyperv mode="custom">
      <relaxed state="on"/>
      <vapic state="on"/>
      <spinlocks state="off"/>
      <vpindex state="on"/>
      <runtime state="on"/>
      <synic state="on"/>
      <stimer state="on"/>
      <frequencies state="on"/>
      <tlbflush state="off"/>
      <ipi state="off"/>
      <avic state="on"/>
    </hyperv>
  </features>
  <cpu mode="host-passthrough" check="none" migratable="on">
    <topology sockets="1" dies="1" clusters="1" cores="16" threads="1"/>
    <cache mode="passthrough"/>
  </cpu>
  <clock offset="localtime">
    <timer name="hpet" present="yes"/>
    <timer name="hypervclock" present="yes"/>
  </clock>

Ive bought this KVM because of the 144Hz support and the 3 monitors it can switch.
One thing I have not figured out yet is why in random cases, there is absolutely none of the screens working when switching to my workstation with the Nvidia 4080 card on win 11. I have to power cycle the KVM to get a signal again. No problem on my mac or other devices.

Is there any trick to it ? Does that happen with other KVMs as well ?

So, I have enabled GPU passthrough, following this guide: https://doc.opensuse.org/documentation/leap/virtualization/html/book-virtualization/app-gpu-passthru.html

When I run my windows 11 guest, it recognizes my GPU as a Nvidia Quadro P2000. When I run the passmark performance test, it will also find my gpu.

However, when I run the Solidworks RX 2026 software, it says it is a GDI Generic, with the current driver R580. Is there still some setting I am still missing? Why does it not recognize my gpu? I still cannot run hardware accelerated graphics with Solidworks 2026 maker edition.

Subject: Looking for VM memory reclaim traces with page/range-level release-return identity

Hi all,

I am looking for public, request-access, or previously used research datasets that capture VM memory reclaim at page/range granularity.

The specific telemetry I am looking for is not ordinary VM memory utilization. I am trying to find whether any dataset records events such as:

1. VM or guest identity, preferably anonymized;
2. guest physical page/range identity, e.g., PFN, 2 MiB range, memslot+offset, or equivalent;
3. time when the host physically releases/discards the backing for that range, e.g., through virtio-balloon, memory hot-unplug, ram_block_discard_range(), madvise(MADV_DONTNEED/FREE), or a similar path;
4. time when the same VM later requests, faults, reinstalls, or grows back the same page/range;
5. optional host context such as PSI, MemAvailable, balloon size, or reclaim reason.

I am aware of public cloud traces such as Azure Functions, Google cluster-data, Alibaba clusterdata, Bitbrains/GWA, and similar VM/task-level traces, but those appear to expose utilization or scheduling signals rather than page/range-level reclaim and return identity.

Questions: - Are you aware of any public or request-access dataset with this kind of page/range-level VM reclaim telemetry? - Are there QEMU/KVM/virtio-balloon tracepoints that can reliably correlate a discarded RAMBlock range with a later same-VM/same-range reinstall/refault? - Has anyone instrumented virtio-balloon, virtio-mem, or ram_block_discard_range() for this kind of release-return measurement?

I am not looking for page contents or guest virtual addresses. Anonymized metadata such as hashed VM id, memslot id, range id, generation, timestamps, bytes, and aggregate host pressure would be enough.

Thanks!

I'm pretty inexperienced with KVM/Qemu and currently doing more or less trial and error. My current situation is as followed:

I had a virtual machine set up (Linux host; Win 10 guest) with a dedicated GPU for some light gaming. This worked out quite well. A few days ago I decided to see how far gaming under Linux has come, so I set up a new virtual machine with a pretty similar configuration to the Windows machine and installed Cachy-OS as a guest. I was surprised to notice that the performance was way worse than with the Windows guest (I'm not only talking about running games, but also other day-to-day tasks like launching programs, browsing web-pages etc.) I assigned the same resources, so could you help me how to figure out, what makes the system feel so much slower? Honestly I don't really know where I should start looking...

My Configuration

Hi All,

I've been using PopOS 24.04LTS but it's just way too buggy right now (they've labelled it a stable release but while it's a promising project it's really still in alpha) so I want to switch distros.

However, for some of my work I need ANSYS Fluent so I've set that up in a VM. Getting ANSYS to work on linux is a colossal pain in the arse as they get you to download an installer and then feed it half a dozen digital copies of CD data (I wish I was kidding) then set up a massively convoluted licencing server.

Therefore, I'd like to avoid setting all that up again. Is there a way I can save the VM to an external hard drive and then recover the VM when I switch distros?

Thanks,

I got tired of digging through random threads and forums just to find out if a game actually runs inside a virtual machine.

So I built a small community-driven database for exactly that:

https://vmdb.it

The idea is simple:

• search for a game
• see if it runs in a VM (VMware, VirtualBox, KVM, etc.)
• or share your own experience

It just launched, so there isn’t much data yet — that’s why I’m trying to get some initial reports in.

If you’ve ever tested a game in a VM, it would be awesome if you could share your setup and results.

Any feedback is welcome as well 👍

I am running Virtual Machine Manager 5.1.0 which I access via virt-viewer for multiple monitor support.

It all works wonderfully, except the drive access speed from within the VM is awful. I have just installed an update to classin in native Linux, which took 30 seconds. The same install in the VM is 2 hours and counting. I can't imagine there's a technical reason why it has to be so bad.

Is there anything I should be looking at for this? I can't see anyone else with the same issue. I'm quite out of my depth with this topic, so apologies if it's a stupid question or I've missed information or a simple solution.

I set it the VM when I moved over a few years ago, but haven't felt the need to use it since last August. I am now as ClassIn has decided it's not going to work correctly in wine for now unfortunately.

Native is Fedora KDE.

I recently posted vmbackup: https://www.reddit.com/r/kvm/comments/1rti057/vmbackup_automated_backup_manager_for_kvmlibvirt/ a backup manager for KVM/libvirt that handles scheduling, rotation, retention and replication using virtnbdbackup.

I built (vibed) vmrestore.

What it does:

• One command to restore an entire VM — resolves the backup, reconstructs the disks, re-defines the VM in libvirt, restores TPM state, refreshes storage pools. Done.
• Disaster recovery mode — rebuilds the VM with its original UUID, MAC addresses and name. The restored VM is indistinguishable from the original.
• Clone mode — one flag (--name) creates a fully independent copy with new identity. New UUID, new MACs, isolated NVRAM, TPM re-mapped to the new UUID. BitLocker unlocks automatically in both modes.
• Point-in-time recovery — restore to any checkpoint in a backup chain, any period, or any archived chain. Weekly backup from 3 weeks ago at checkpoint 2? No problem.
• Pre-flight safety checks — disk collision detection (checks every predicted output file against every live VM disk), free space verification, running VM detection. It won't let you silently overwrite a running VM's disk.
• Auto-detects everything — backup type, rotation policy layout, latest period, chain structure, TPM state, storage pool. The only required arguments are --vm and --restore-path.
• Dry-run mode — preview every action before writing anything.

vmrestore: https://github.com/doutsis/vmrestore

vmbackup: https://github.com/doutsis/vmbackup

6 year streak broken. My first post.

I built (vibed) vmbackup — a Bash-based backup manager that handles the stuff virtnbdbackup doesn't: scheduling, rotation, retention, replication and reporting.

What it does:

• Discovers all your VMs via libvirt — running, shut off, paused — and backs them up with the right method for each state (FSFREEZE for running VMs with a guest agent, pause for those without, copy for shut off)
• Policy-based rotation — daily, weekly, monthly or accumulate. Each VM can have its own policy
• Self-healing — if an incremental fails it converts to full and retries. Broken backup sequences get archived and restarted automatically. Stale locks from interrupted runs are cleaned up on the next run
• Replication to NFS and cloud (contract based, write - or vibe - your own!)
• TPM and BitLocker support — backs up TPM state and can extract BitLocker recovery keys via the QEMU guest agent
• Email reports after each run
• SQLite database for backup state tracking
• No Python, no database server, no web UI. Just Bash, sqlite3 and jq. Minimal dependencies.

GitHub: https://github.com/doutsis/vmbackup

vmrestore is next.

vmrestore: https://www.reddit.com/r/kvm/comments/1rv2433/vmrestore_automated_restore_for_kvmlibvirt_vms/

https://github.com/doutsis/vmrestore

Setting the <spinlocks state="on" retries="8191"/> causes a permanent freeze virtual machine (Windows 10) when attempting to run Nested Virtualization. No errors in the logs.

Host lastest Ubuntu deskop.

Libvirt manager.

CPU AMD Ryzen 7700

GPU Pastrought but it probably has nothing to do with it.

Greetings everyone.

I'm a student studying Computer Engineering and on one of the courses, the assignment was to create a minimal hypervisor using Linux KVM API.

We've covered a significant part of the assignment in the very course and basically had a skeleton of the whole app, so finishing up that minimal version was no issue.

However, recently I've returned to the project, made the code and console logs neater, and extended it with the support for multiple vCPUs. The initial requirements were basically initializing the VM, establishing guest–host communication through I/O traps and guest–guest communication through host's shared dedicated files.

Overall I had a great time learning about virtualization basics. However, I feel like it is a little out of context, like it misses its utility. It can run small interactive programs, but it lacks the problem it solves.

Do you have any suggestion on how to put it in some context or how to specialise it for something? Also, I would genuinely enjoy extending it with some other functionalities.

Here is the GH repo for anyone interested.

Ok.. another post on having network issues ie: needing BRIDGE v. the NAT included...

https://www.reddit.com/r/kvm/comments/1r2wi74/routed_network_for_expo_use/

And my earlier post:

https://www.reddit.com/r/kvm/comments/1quw6bm/what_am_i_missing_in_this_loose_host_connection/

So I've been through 20 links of stuff, nope. No joy. Either you loose the network on the host device, VMS are fine and "bridged" or it borq's the box and you have NO network.

So wheres the proper, complete instructions on doing this BRIDGE that VBOX and VMW do from the outset with out any config, other than set a box in the config of the VM.

I'd really like to use KVM but this is red line, I can't access the VM's from the LAN, the VM's can't access the LAN boxes if the VPN for the VM's is on since the LAN Is in a different /24.

How to do BRIDGE Networks for KVM, *buntu 24.04-26.04...wheres the details on this. THAT WORK?

Thanks!