VMware Workstation
root@router:~# dmidecode -s system-product-name
VMware Virtual Platform
VirtualBox
root@router:~# dmidecode -s system-product-name
VirtualBox
Qemu with KVM
root@router:~# dmidecode -s system-product-name
KVM
Qemu (emulated)
root@router:~# dmidecode -s system-product-name
Bochs
Microsoft VirtualPC
root@router:~# dmidecode | egrep -i 'manufacturer|product'
Manufacturer: Microsoft Corporation
Product Name: Virtual Machine
Virtuozzo
root@router:~# dmidecode
/dev/mem: Permission denied
Xen
root@router:~# dmidecode | grep -i domU
Product Name: HVM domU