Double fault is when the PE receives another error whilst one is being
handled. To detect double fault condition, a per-CPU flag is introduced
to track the status of error handling. The flag is checked/modified
while temporarily masking external aborts on the PE.
This patch routes double faults to a separate platform-defined handler.
Change-Id: I70e9b7ba4c817273c55a0af978d9755ff32cc702
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
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