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Re: [MiNT] fVDI issues

Hello!

> Perhaps it would be a good idea if the VDI and AES developers talked
> a bit about what we want/need from this kind of functionality in MiNT?
> And, of course, it would be good if the MiNT kernel developers could
> describe what thoughts they have about this kind of interface.

The idea is that it integrate the VDI and AES easily into the kernel, not
to make anything harder :-)

> > Entering the kernel is an expensive operation, also for routines that just
> > consist of one line (getpid and these things).
>
> I'm well aware of that, and have complained about it before.  ;-)
>
> So, at least for the VDI, fully entering the kernel (build_context etc)
> is not really an option, IMHO.

The kernel entering is not only done for fun, there are requirements to
fullfill.

> At least not unless deemed necessary
> after return from the VDI code (for example if the time slice is up).
> It doesn't really matter if getpid() takes a long time, since it's not
> called often. And the same applies to most (all?) of GEMDOS/BIOS/XBIOS,
> and probably the AES.

Yes, AES is the same category as GEMDOS. VDI may be used more frequently
for sure.

> Many often called VDI routines can make do with only a couple of
> registers saved on the stack. None of them pass any parameters on the
> stack. None of them, AFAICR, would have any reason to ever require a
> process to suspend.

Can these simple calls put into user space? E.g. does they work without
any hardware access and without any critical, VDI global data?

> Does MiNT currently do anything about pointers passed to system calls
> under memory protection, by the way?

Not really.

> Actually, it would make sense to make parts of the VDI actually execute
> in user mode. It's unfortunate that we're stuck with the Trap #2.

But you need to go back to userspace after the Trap.


Ciao
   ...Frank

--
ATARI FALCON 040 // MILAN 060
-----------------------------------------
http://www.cs.uni-magdeburg.de/~fnaumann/
e-Mail: fnaumann@freemint.de