1.How is the exception level of armv8 created for initialization?It seems that only the initialization of el3 is available here？
2.Is there any way to implement multi-core boot in BL phase (for multi-core devices)?Is it changing the data of "_secondary_cold_boot" above?
Q1) EL3 is the highest Execution Level (EL) of Armv8-A processors. So TF-A will enter el3 first except special cases.
Q2) Usually single core boot can give the software developers an easy life when designing the bootloader. Any special requirements for you to support the multi-core boot up?