The HPT contents for the crashed OS must be kept unchanged so that diagnosis can be made. To preserve these HPT contents, the hypervisor saves the first 8MB of HPT entries into ALDR-memArea, and limit the size of the HPT to 8MB before activating ALDR-AIX; i.e. we restrict ALDR-AIX to run with only the first 8MB of HPT entries.
However, to enable ALDR-AIX’s kernel debugger to access all the memory locations used in the original OS (so as to
perform diagnosis), we created a new hypervisor call for ALDR-AIX’s kernel debugger to access those HPT entries
that are beyond the first 8MB. Additionally, any access to virtual I/O devices is disabled during the operations of the
repair image to prevent virtual devices from changing any state. This is accomplished through a new hypervisor call
that is issued right before invoking ALDR-AIX.