It seems that the linux.dtb file supplied with the tutorial code is not
correct and does not allocate enough memory for the initrd. The symptoms
this issue caused when attempting to run part4 was that the
libresolv.so.2 could not be opened and the vmm panic'ed. The linux.dtb
supplied in the 'solution' folder in the git repository has 'initrd-end'
set to a larger value and this version does work.