Sometimes it is helpful to be able to mount an image under the host system. If you wish to mount a QEMU / KVM disk image you could use qemu-nbd.
First you need to load the module:
sudo modprobe nbd max_part=8
Then you can share the disk on the network and create the device entries:
sudo qemu-nbd --connect=/dev/nbd0 file.qcow2
Then you mount it:
mount /dev/nbd0 /mnt
When done, unmount and unshare it:
umount /mnt/kvm nbd-client -d /dev/nbd0
NB: never mount a QEMU image while QEMU is using it (unless -snapshot is used), or you are likely to corrupt the filesystem on the image.