7-8 PPC405 Core User’s Manual
and translation is disabled. If the operating system simply made the TLB updates and returned from
the handler (using rfi or rfci), no additional explicit software action would be required to synchronize
the ITLB and DTLB.
If, instead, the operating system enables translation within the handler and then performs TLB
updates within the handler, those updates would not be effective in the ITLB and DTLB until rfi or rfci
is executed to return from the handler. For those TLB updates to be reflected in the ITLB and DTLB
within
the handler, an isync must be issued after TLB updates finish. Failure to properly synchronize
the shadow TLBs can cause unexpected behavior.
Programming Note: As a rule of thumb, follow software manipulation of an translation
mechanism (if performed while translation is active) with a context-synchronizing operation
(usually isync).