Windows | 7qcow2

qemu-img convert -f qcow2 win7.qcow2 -O raw win7.raw

qemu-img convert -f vpc -O qcow2 windows7.vhd windows7.qcow2

virsh snapshot-revert win7 before_patches

| Setting | Recommendation | |---------|----------------| | Disk bus | VirtIO (best performance) | | Cache | writeback or unsafe (for speed) | | CPU | host passthrough (-cpu host) | | QEMU agent | Install qemu-ga in Windows 7 for better integration | windows 7qcow2

Run QEMU with these optimized parameters:

qemu-system-x86_64 \
  -drive file=windows7.qcow2,if=virtio,format=qcow2 \
  -cdrom /path/to/en_windows_7_professional_x64.iso \
  -cdrom /path/to/virtio-win.iso \
  -m 4G \
  -cpu host \
  -smp 4 \
  -netdev user,id=net0 \
  -device virtio-net-pci,netdev=net0 \
  -usb -device usb-tablet \
  -vga qxl \
  -machine type=q35,accel=kvm

Critical notes for Windows 7:

echo 1 > /sys/kernel/mm/ksm/run

This is the killer feature for Windows 7 testing. Keep one pristine windows7-base.qcow2 (read-only) and create multiple overlay images. qemu-img convert -f qcow2 win7

Create the base (DO NOT boot this directly):

qemu-img create -f qcow2 windows7-base.qcow2 40G
# Install Windows 7 on this base

Create an overlay for testing:

qemu-img create -f qcow2 -b windows7-base.qcow2 -F qcow2 test-instance1.qcow2

Now run test-instance1.qcow2. All writes go to the overlay; the base remains untouched. To discard changes, delete the overlay and create a new one.