Hi, I am new to ARMv8 architecture and while reading the v8 exception vectors I am not able to understand significance of adding SP_EL0 level vectors while SP_ELx vector set exists. What I am trying to find a use case where this is useful. I understand that when the exception is taken at same level by default the stack of same exception level is used for example if EL2 (Hyp) mode is defined then if exception occurs while being at EL2 level the stack defined at EL2 will be used but not sure if I configure to use EL0 level stack under what use cases this could be useful ? Can some one give a use case and explain ? Also while going through the spec it seems these two different stack usage idea is taken from Cortex-M architecture but i am not very clear with thread and handler modes as well. Can any one explain it ? Just wanted to add here that ARMv7 doesn't have thread and handler concept so i am not clear requirement in ARMv8. Also in ARMv7 my understanding is that stack pointer for exceptions eg. if IRQ occurs in Hyp mode then banked IRQ_SP is used so no need to specify the SP.
Thanks