In fasmg additional passes are only very slightly faster than the first one, so the total time is roughly the multiple of a single pass.

Listing macro, as the name implies, is just a macro. It gets processed every time the source code is processed, just like any other macro.

How does it limit to one listing copy, not one per pass ?

namespace Listing
        base = $$ 
        offset = $
        virtual at 0
                HexDigits:: db '0123456789ABCDEF'
        end virtual
        macro disphex number*,digits:8
                repeat digits 
                        load digit:byte from Listing.HexDigits:((number) shr ((%%-%) shl 2)) and 0Fh
                        display digit
                end repeat
        end macro 
end namespace