How to know which core that send the inter-processor interrupt?

I am working on ARM64. I add an inter-processor interrupt (IPI) handler in void handle_IPI(int ipinr, struct pt_regs *regs) in linux/arch/arm64/kernel/smp.c.

When I get an IPI, I want to know which core sends this IPI. For example, core 3 sends an IPI to core 0, then core 0 gets the IPI, I want to know that this IPI is from core 3 in the IPI handler.

Is there a way to do it?

Thanks a lot.