FOSDEM talk next week

[bartoldeman]

Hi,

as the mailing list is not so active I am abusing an issue for this request. Next week I will be at FOSDEM (also for other work-related reasons) and will talk about DOSEMU and FreeDOS:
https://fosdem.org/2018/schedule/event/dosemu_and_freedos_past_present_future/
I can talk a little bit about DOSEMU2. Apart from looking for highlights in the NEWS file, is there anything important you (Stas) would like me to mention?

Also, to others who are subscribed to the issues, any cool applications you know of DOSEMU?

By the way I haven't tried it yet with a Meltdown/KPTI enabled kernel but can't imagine those are very friendly to DOSEMU...

[stsp]

Why is this all happens while I am
working on a freedos fork? :) I am sure
there would be much more interesting
things to talk about, but its not there yet.
Just to give you some numbers, I have
currently:

94 files changed, 3651 insertions(+), 1487 deletions(-)

And this is of course not counting the
white-space noise of this PR:
PerditionC/fdkernel#14
which would otherwise give a diffstat of

147 files changed, 5199 insertions(+), 3078 deletions(-)

But don't worry, I will not call it "freedos2",
the name which is mentioned as your fosdem topic.

As for dosemu2 itself, the highlights can be
extracted from here:
https://github.com/stsp/dosemu2/releases
or from NEWS.
The things that are not mentioned in NEWS/releases,
are: the fully rewritten video stack with SDL2, much improved
sound stack, mostly rewritten sighandling and DPMI
context switching, better EMS support (with paging of
lowmem).
One thing that definitely deserves a talk, is a way
I now support win32 under HX extender. There is
a famous problem with mapping win32 binaries at
a fixed address that may be unavailable because
of the memory layout randomization. Wine worked
around this by AFAIK writing the custom ld.so -
wineloader. dosemu2 solves this much better: I
just reserve some mem after lowmem itself, and
this reserve is always available for DPMI linear
mappings. Thanks to your non-zero mem_base
trick, this costed nearly nothing. So we have a
fully functional relocation machinery that is based
only on LDT segment base! No custom preloaders!
I even enabled pie, and it still works.

There are a few commercial deployments of dosemu2
that I am aware of. Namely, it is used in a POS
terminals with some commercial MUMPS interpreter:
https://en.wikipedia.org/wiki/MUMPS
For that I had to add an advanced EMM support,
as this interpreter has the built-in multitasker and
memory pager. dosbox doesn't support that, but
it probably can be easily added there.
Another application was some saw controller on
a furniture factory. For that I wrote a support for
custom serial port boards. Also I think @bolle732
uses it commercially for running GEOS:
https://en.wikipedia.org/wiki/GEOS_(16-bit_operating_system)
for which we had many VESA modes emulation fixes
as well as the EMM fixes.

Essentially I think dosbox could adopt these
things too, but it refused to do so, as it is only for
games. One thing it can't adopt though, is speed.
dosemu2 is much faster, except for 2 cases:
PIT emulation is bad, so progs that calculate
delays based on PIT counters sampling (rather
than based on PIT interrupts) are horribly slow.
Plus I've got a very slow emulation of unchained
VGA mode (compared to both dosemu1 and dosbox).

By the way I haven't tried it yet with a Meltdown/KPTI
enabled kernel but can't imagine those are very friendly to DOSEMU...

Forget it. :) They are not enabled on AMD processors
by default any longer, as AMD processors are immune to this.
And future Intel CPUs will likely be too. Plus, the meltdown
threat is exaggerated by miles. It is not even nearly
as big as the media claims it is. In a nutshell, it allows
you to steal only the memory that is already in an L1 cache -
not more, not less. The reliable ways of prefetching an
arbitrary kernel memory into L1 cache are yet to be seen.

[bartoldeman]

Thanks for the comments. I've got quite a bit to work with now combined with the ML reactions.

As for FreeDOS 2.0, it's just a proposal/discussion for a FreeDOS distribution that succeeds FreeDOS 1.2, not the kernel, see https://sourceforge.net/p/freedos/mailman/message/36080115/

Looking at your github are you talking about your gcc branch that probably works with plain gcc (using protected mode?) instead of needing tkchia's ia16-elf-gcc branch right?

I've so far managed to compile the kernel (changed merged into github) and freecom (still on svn) with ia16-elf-gcc. Generated code not as small as Open Watcom yet, but passable (slightly better than Turbo/Borland).

[stsp]

Yes, that's the basic idea.
I want a fully protected mode DOS.
Of course this may not happen as
its widely accepted as impossible
wrt the freedos codebase. But was
this ever the reason not to try. :)

[stsp]

Hmm, oh, a Retrocumputing devroom on fosdem...
Time flies too quickly.
Maybe if we code up a prot mode DOS, then next
time you can qualify for an Embedded devroom
or Virtualization devroom instead? :)

[bolle732]

Regarding PC/GEOS:
Yes, it's currently still a commercial product. The new owner plans to make as much as possible open source. But when and how is still up to the stars. There is a topic on a German forum about this: http://geos-infobase.de/WBB_317/index.php?page=Thread&threadID=2469

Myself, I use PC/GEOS only for personal pleasure. Like others that run Windows 3.11 under DOSEmu(2).

Some times, I do little programs to run under PC/GEOS in GOC (C extended by a proprietary object oriented system) or R-Basic. There are still a handful people doing so.

Further, I help some of the last Mohicans using PC/GEOS. I know about 10 users running it under Linux / DOSEmu2. This users are mostly not too deep technical affine. But they switched from pure DOS or Windows to Linux, because DOSEmu(2) supports PC/GEOS very well.

In my eyes, DOSEmu2 provides the most stable and fastest environment for PC/GEOS. Especially on 64-bit systems when using KVM. And in this regards, KVM is really the way into the future.

Last, I would thank the DOSEmu(2) developers in the name of all PC/GEOS users. Still, there is room for some improvement. Only that the real life is currently eating all my free time. But I never loose the hope ;-)

[stsp]

Regarding PC/GEOS:
Yes, it's currently still a commercial product. The new
owner plans to make as much as possible open source.

You mean, open-source geos itself, or something else?

Like others that run Windows 3.11 under DOSEmu(2).

Correction: Windows 3.1 under dosemu2.
Other combinations (3.11 under dosemu1 etc) are not viable.

Thanks for the good feed-back!

[stsp]

And in this regards, KVM is really the way into the future.

I don't think this is technically true.
KVM offers a lot of machinery to accelerate
the ring-0 system code, but dosemu doesn't
use those. For example, we don't need
nested page tables, which is the biggest
thing of KVM. For our needs the good jit
engine could do similar or even better job.
Unfortunately, writing the good jit engines
is not something we have the resources for.
So KVM is the way into the future, but its
not the best possible one, as being not portable.
Of course its great that we have it right now.
Maybe one day there will be a good jit around
for us to steal. :)

[bolle732]

You mean, open-source geos itself, or something else?

Yes, almost any parts of kernel, drivers and application should be open sourced. They are still reviewing the source code regarding third party licenses like the font system or thesaurus which can't be open sourced. But as we all know, open source is not equal to GPLx or any other free license. So that would be the interesting statement I'm still waiting for...

Correction: Windows 3.1 under dosemu2.
Other combinations (3.11 under dosemu1 etc) are not viable.

Thank you for the correction. I haven't done a lot with Windows 3.x.

[jschwartzenberg]

Damn, next week already I should've paid more attention to FOSDEM. If there'll be a dosemu talk again next year I'll definitely come to Brussels.

[andrewbird]

Perhaps it will be videoed?

[stsp]

https://video.fosdem.org/2018/

[stsp]

Another interesting thing for fosdem may
be to run win95 under dosemu2, like this:

[stuaxo]

Wow, when did this start working?

[stuaxo]

Doh, just noticed its Calimera, hehe.

[bartoldeman]

I can show the screenshot, but what's Calimera exactly? Google did not find much.