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QEMU

Is a Virtual Machine Software

CPU Model

  • CPU features per level (v1 → v4) for x86
    • v3: AVX, AVX2, …
    • v4: AVX-512

Flags

Best settings when creating a VM

  • Windows 10 guest best practices
  • System
    • QEMU Agent: enabled
    • Machine type: q35 + BIOS: OVMF for PCI Passthrough, otherwise default is fine
  • CPU
    • Type:
      • x86-64-v4 works fine
        • better than host for Windows as it signal that the machine is a VM
      • ⚠️ Don't use host, at least on Proxmox
        • decrease memory performance
        • match the Host CPU
        • impact migration to to other systems
    • vIOMMU
      • Intel has slightly better memory latency
  • Memory
    • Ballooning: enabled, disable on Windows
    • Minimum memory: don't use on Windows
    • 1 GB must be made available for the host
  • Network
    • Type: VirtIO
  • Display
    • Type: std or qxl for SPICE
  • Firmware
    • SeaBIOS by default
    • OVMF for Windows 11 and PCI Express
      • pre-enroll-key for Windows keys + Secure Boot on
      • Virtual screen resolution is set in the VM BIOS
  • Storage
    • Controller: VirtIO SCSI (source) single with IO Thread enabled
    • Image Format: raw disk image by default if you use LVM or ZFS
    • Cache: none (source)
      • writeback is faster, but can result in data lose
    • Discard: enabled + SSD emulation: enabled, to let the OS TRIM
    • IO Thread: enabled
  • For Windows