Now I'm considering migrate from Xen to KVM. I exported some exist virtual machines from Xen in the formats
xva. How could I import them into KVM?
As there're only a few of virtual machines, I would accept a manual way.
The following is a straight quote from the Red Hat 6 help link, in case it fails. It seems everything is based on using virt-v2v now, and doing an offline xva to kvm isn't so simple. Try the virt-v2v man pages.
Where vmhost.example.com is the host running the virtual machine, pool is the local storage pool to hold the image, bridge_name is the name of a local network bridge to connect the converted virtual machine's network to, and guest_name is the name of the Xen virtual machine.
You may also use the --network parameter to connect to a locally managed network if your virtual machine only has a single network interface. If your virtual machine has multiple network interfaces, edit /etc/virt-v2v.conf to specify the network mapping for all interfaces.
If your virtual machine uses a Xen para-virtualized kernel (it would be called something like kernel-xen or kernel-xenU) virt-v2v will attempt to install a new kernel during the conversion process. You can avoid this requirement by installing a regular kernel, which will not reference a hypervisor in its name, alongside the Xen kernel prior to conversion. You should not make this newly installed kernel your default kernel, because Xen will not boot it. virt-v2v will make it the default during conversion.