Some questions about Fiasco

[Michael Hohmuth]

Benjamin Gerfelder <benjamin at dante.saar.de> writes:

> I just succeeded in booting Linux on Fiasco. Just in case anyone
> is interested, here are the warnings I got while booting:

[ warning messages appended below for reference ]

Congratulations for getting it up!

All of the bootup warning messages are normal (and probably should be
removed from the code base).

> [...] I just get *a lot of*
> 
> wake_idle_if_needed: ipc failed
> 
> messages, but this seems to be no problem. 

We decided to not remove this L4Linux warning message in this release
because we think it hints at a potential problem; at least we don't
get this message under Jochen's L4/x86.  I have to discuss this some
more with my colleagues...

> The only thing I`ve found that doesn`t work is XFree86, when I try
> to start it, the machine freezes with blank screen.

A remote debugger or a second (Hercules) video card would be of help
here.

One idea I have is that maybe we don't see these hangs because we let
Fiasco send the "ipc failed" warning messages to the Hercules screen
instead of the VGA console.  Perhaps XFree86 crashes when someone else
fiddles with the video memory?  I'll try this out.

> 1) Are there any documents you suggest reading, besides the L4 Reference
>    Manual? Any document would be of use, since I don`t have a clue on
>    L4, but I want to play around with it. Is there anything like
>    "L4 for dummies" ? :)

UNSW has an L4 User's Guide which covers MIPS L4, but some people have
said it's interesting from an x86 perspective, too; see
<URL:http://www.cse.unsw.EDU.AU/~disy/L4/l4uman.ps.gz>.

Other than that, I suggest you read some (depending on your interest)
papers about L4 and L4Linux at
<URL:http://os.inf.tu-dresden.de/pubs/#l4linux>.

Unfortunately, something like an ``L4 for dummies'' doesn't exist.

> 2) Is Fiasco capable of running multiple servers at once?

Yes, this is possible.  

>    I tried to start two instances of this helloworld-server, but it
>    crashed immediately.

This doesn't work because Rmgr, the boot-up server and resource
manager, is not a sophisticated memory manager.  It can only run
servers which want a one-to-one physical-to-virtual virtual-memory-
space mapping.  You example would work if the two instances of "hello" 
were linked to different virtual memory locations.

As an example which works out of the box, try running "hello" and the
L4Linux server parallelly.

> 3) Is there a simple way to reboot the system after Fiasco startet?
>    My Laptop has no reset button :)

No, there isn't, unless your program does it for you.  For instance,
L4Linux uses the keyboard controller method to reset the machine when
it shutdowns; this arguably is not the ``correct'' solution to this
problem.

Does anyone have a good idea for an interface to reset the machine in
the normal and exceptional cases?


Greetings,
Michael

> -----------------------------------
> Welcome to Fiasco!
> DD-L4/x86 microkernel (c) 1998 TU Dresden - Dec 24 1998
> linux_startup
> checking OFFS_TSS: ok, OFFS_TSS still 536
> detect processorsetup_paging
> end linux_startup, calling start_kernel
> setup_arch
> sigma0 denies mapping of address 00001000
> No kernel code/data
> sigma0 denies mapping of address 00002000
> No kernel code/data
> [...]
> sigma0 denies mapping of address 00149000
> No kernel code/data
> 
> mb4 already requested
> 
> 4m page received
> sigma0 denies mapping of address 00ccc000
> No kernel code/data
> 
> Memory end: 00ccc000
> 
> kernel info page mappt to: 00001000
> root: rcvd 2, 424a25
> Hmm, strange, that shouldn't happen anymore
> Root: null pointer deref in 5.3 at addr: 2 and eip: 424a25 (pte: 27)
> -------------------------------------

-- 
hohmuth at innocent.com, hohmuth at inf.tu-dresden.de
http://home.pages.de/~hohmuth/