Subject: Use of TSS
To: None <>
From: Charles Hannum <>
List: port-i386
Date: 11/13/1993 14:35:57
I'm considering whether it is worthwhile to use a TSS per process or
not.  Currently, we allocate space for a TSS in each PCB.  My plan
would be to use a single GDT slot and simply poke a new TSS descriptor
in before we switch; that way we don't have an increasingly large GDT,
and we are not arbitrarily limited to 8180+change processes (not that
I expect to see this many, mind you).

The advantage here is that we could give fine-grain control of what
I/O ports a process is allowed to use; i.e. a process which opens
/dev/vga only gets the I/O ports for /dev/vga.  Also, the task
switching code would be much simpler, as most of the work would be
done by the processor.  The disadvantage is that it will probably be a
little slower than the current task switching code.