The ASID allocator has to deal with some pretty horrible behaviours by
the CPU, so expand on some of the comments in there so I remember why
we can never allocate ASID zero to a userspace task.
Reviewed-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>