Figure 1 shows a high-level overview of ALDR. Each
POWER server runs one or more guest OSes or LPARs
using the PHYP hypervisor. The AIX LPARs require a
small portion of the kernel space memory to be accessed
in address-translation-off mode. This region, called RMA
(Real Mode Area) is used by OS boot code before translation
tables are set up, by the translation-fault handling code
during run time, and by a small part of firmware called PFW
(Partition FirmWare) that acts as a glue between the kernel
and the hypervisor. The POWER architecture also allows
RMA to be virtualized by the hypervisor in which case this
region is called VRMA. The VIOS LPAR [8] enables the
sharing of physical I/O resources across the VIOS-client
LPARs within the same managed server. ALDR currently
relies on the VIOS to enable quick and efficient suspension
and restart of shared physical I/O and network resources.