cpu_vm_mask checks in ARM flush functions

[muni anda]

I was going though the cache flush functions in arch/arm/mm/flush.c
and found that cpu_isset() is used at a lot of places. I couldn't
understand the reason why there is a need for cpu_vm_mask checks? My
understanding was that those functions will be executed on the CPU for
which the cpu_mask is already set (in switch_mm call). Is there a
different calling sequence that I am missing?

Can someone please the need for those checks (For example
flush_ptrace_access() function running on vipt_non_aliasing caches).

Thanks,
-Muni