small address-space can not be used in em64t mode ?

[coly]

Hi, The transparently flexing user address space method which is called
as "small address-space" uses segment to implement the protection for
small address sapce.

But in em64t or amd64 mode, there is not segment (except FS,GS) exists.
So it seems the small address-space method can not be used under 64bit
mode. Isn't it ?

Thanks in advance.

Coly