Because you perform a syscall, say for I/O, and tell the kernel: Hey, put
this into this buffer. Now, what woul the kernel do, if the memory is not
mapped? How should the kernel start a binary, if it can not access the
memory, where it's started.
If the kernel does not map the memory, it cannot control it.
The only way out is to use other selectors and to have context switches,
which would hurt performance, as said before.
I don't think, that's what we want.
-- Kurt Garloff <kurt@garloff.de> [Dortmund, FRG] Plasma physics, high perf. computing [Linux-ix86,-axp, DUX] PGP key on http://www.garloff.de/kurt/ [Linux SCSI driver: DC390]- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/