Re: [f-cpu] little feed-back from the libre softawre meeting

[Michael Riepe <michael@stud.uni-hannover.de>]

On Sat, Jul 13, 2002 at 01:30:45AM +0200, whygee@club-internet.fr wrote:
[...]
> >     read, write, exec bit + at least 3 rings (super user + user +
> >     something like for library,...)
> 
> RWX is ok, because this is how protection is enforced.
> i'd say that it is the minimum required TLB feature.

*nod*

What about different permission bits for different protection levels?
Like `supervisor may read and write, j. random luser may only read'.
That's probably better than a `user/supervisor' bit or an explicit
`page protection level'.

> Concerning rings and groups, the issue is still open,
> as several proposal and ideas are floating and careless
> design will turn F-CPU implementations into a VAX-like,
> or worse... helping SW and OS is ok, as long as we don't
> do in HW all the work. It must be also "friendly" with
> many OS approaches, so i choose the "least common denominator"
> approach. A TLB with RWX rights and VMID is the most common
> feature and it's straight-forward to understand for SW and
> HW design. I'll try to continue to speak with the OS guyz
> (linux, Hurd and *BSD) to sort this.

Misquoting Bill Gates:

	`Two protection levels should be enough for every OS.'

[...]
> >>From my view,
> >     none polling thread barrer should be implemented (for tigh
> >     multithreaded application on multicpu)
> 
> please rephrase that and spellcheck it, i did not understand.

He probably meant: a non-polling thread barrier should be implemented for
`tight' multithreading. I'm not sure what he means with `thread barrier',
though - something like a hardware semaphore?

-- 
 Michael "Tired" Riepe <Michael.Riepe@stud.uni-hannover.de>
 "All I wanna do is have a little fun before I die"
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