Tested on the image linked from the wiki:
https://wiki.qemu.org/Testing/System_Images
Boot after decompressing with:
or1k-softmmu/qemu-system-or1k -cpu or1200 -M or1k-sim \
-kernel path/to/or1k-linux-4.10 \
-serial stdio -nographic -monitor none
Thanks,
Emilio