[Qemu-devel] Report

[Qemu-devel] Report

[Nigel Horne]

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Folks,

Thanks for qemu. I thought you may like to know that from a Linux x86 host
I have 3 linux guests: sparc, arm and mips. The first 2 work a treat, the
mips keeps core dumping in libc6 when called from Perl, I don't know if
the problem lies in libc6, perl or qemu.

Can qemu emulate 16-bit machines (286?)?

-Nigel

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[Qemu-devel] 16-bit (and 8-bit) emulation

[Stuart Brady]

On Sun, Apr 15, 2007 at 11:08:56AM +0100, Nigel Horne wrote:
> Can qemu emulate 16-bit machines (286?)?

None that I'm aware of.  Is there any particular need for 286 emulation?
OTOH, it might be interesting to see some m68k system emulation.

I've been working on an 8-bit machine, with some success.  The one thing
that I'm not really sure about is bank switching (although I think I can
just call cpu_register_physical_memory()).

HTH,
-- 
Stuart Brady

Re: [Qemu-devel] 16-bit (and 8-bit) emulation

[Paul Brook]

On Sunday 15 April 2007 12:33, Stuart Brady wrote:
> On Sun, Apr 15, 2007 at 11:08:56AM +0100, Nigel Horne wrote:
> > Can qemu emulate 16-bit machines (286?)?
>
> None that I'm aware of.  Is there any particular need for 286 emulation?
> OTOH, it might be interesting to see some m68k system emulation.
>
> I've been working on an 8-bit machine, with some success.  The one thing
> that I'm not really sure about is bank switching (although I think I can
> just call cpu_register_physical_memory()).

It's probably easier to map all banks into a single large address space, and 
use the bank number as the high bits of the address. That way you can switch 
banks without having to flush everything.

gdb uses similar tricks to deal with multiple address spaces on DSPs.

Paul

Re: [Qemu-devel] 16-bit (and 8-bit) emulation

[Nigel Horne]

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Stuart Brady wrote:
> On Sun, Apr 15, 2007 at 11:08:56AM +0100, Nigel Horne wrote:
>> Can qemu emulate 16-bit machines (286?)?
> 
> None that I'm aware of.  Is there any particular need for 286 emulation?

To test my code on machines where sizeof(int) == sizeof(short), and
sizeof(int) != sizeof(long).

> OTOH, it might be interesting to see some m68k system emulation.

I can't remember now what sizeof(int) and sizeof(char *) were on m68k machines.

-Nigel

-- 
Nigel Horne. Arranger, Adjudicator, Band Trainer, Composer, Tutor, Typesetter.
NJH Music, Barnsley, UK.  ICQ#20252325
njh@bandsman.co.uk http://www.bandsman.co.uk

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Re: [Qemu-devel] 16-bit (and 8-bit) emulation

[Paul Brook]

On Sunday 15 April 2007 13:08, Nigel Horne wrote:
> Stuart Brady wrote:
> > On Sun, Apr 15, 2007 at 11:08:56AM +0100, Nigel Horne wrote:
> >> Can qemu emulate 16-bit machines (286?)?
> >
> > None that I'm aware of.  Is there any particular need for 286 emulation?
>
> To test my code on machines where sizeof(int) == sizeof(short), and
> sizeof(int) != sizeof(long).

Modern x86 are backwards compatible[*], so you should be able to do that 
anyway.

Paul

[*] There are a few corner cases, but these are only likely to effect 
hand-written asm doing evil things. There's probably more difference between 
qemu and real hardware than 286 and i386 real mode.

Re: [Qemu-devel] 16-bit (and 8-bit) emulation

[Nigel Horne]

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Paul Brook wrote:
> On Sunday 15 April 2007 13:08, Nigel Horne wrote:
>> Stuart Brady wrote:
>>> On Sun, Apr 15, 2007 at 11:08:56AM +0100, Nigel Horne wrote:
>>>> Can qemu emulate 16-bit machines (286?)?
>>> None that I'm aware of.  Is there any particular need for 286 emulation?
>> To test my code on machines where sizeof(int) == sizeof(short), and
>> sizeof(int) != sizeof(long).
> 
> Modern x86 are backwards compatible[*], so you should be able to do that 
> anyway.

Care to share with us how I do that? Is it an option to gcc?
> 
> Paul



-- 
Nigel Horne. Arranger, Adjudicator, Band Trainer, Composer, Tutor, Typesetter.
NJH Music, Barnsley, UK.  ICQ#20252325
njh@bandsman.co.uk http://www.bandsman.co.uk

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Re: [Qemu-devel] 16-bit (and 8-bit) emulation

[Paul Brook]

> > Modern x86 are backwards compatible[*], so you should be able to do that
> > anyway.
>
> Care to share with us how I do that? Is it an option to gcc?

gcc does not support 16-bit mode.

My point is that pretty much anything that runs on a 286 should also run on 
any subsequent x86 processor. If you want to test 16-bit x86 software/systems 
you don't need an actual 286. A 386 is just as good for almost all purposes.

Paul

Re: [Qemu-devel] 16-bit (and 8-bit) emulation

[Nigel Horne]

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Paul Brook wrote:
>>> Modern x86 are backwards compatible[*], so you should be able to do that
>>> anyway.
>> Care to share with us how I do that? Is it an option to gcc?
> 
> gcc does not support 16-bit mode.
> 
> My point is that pretty much anything that runs on a 286 should also run on 
> any subsequent x86 processor. If you want to test 16-bit x86 software/systems 
> you don't need an actual 286. A 386 is just as good for almost all purposes.

How does that address my issue?

> Paul

-Nigel

-- 
Nigel Horne. Arranger, Adjudicator, Band Trainer, Composer, Tutor, Typesetter.
NJH Music, Barnsley, UK.  ICQ#20252325
njh@bandsman.co.uk http://www.bandsman.co.uk

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Re: [Qemu-devel] 16-bit (and 8-bit) emulation

[Paul Brook]

> > My point is that pretty much anything that runs on a 286 should also run
> > on any subsequent x86 processor. If you want to test 16-bit x86
> > software/systems you don't need an actual 286. A 386 is just as good for
> > almost all purposes.
>
> How does that address my issue?

You wanted a 286 so that you could test 16-bit x86 code. You can already do 
that with current qemu. How you generate that 16-bit x86 code is a completely 
unrelated (and offtopic) problem.

Paul

Re: [Qemu-devel] 16-bit (and 8-bit) emulation

[Nigel Horne]

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Let me approach this in a different way in the hope that I'll get an answer to my
question: will Qemu run a 286 guest O/S?

-Nige

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Re: [Qemu-devel] 16-bit (and 8-bit) emulation

[Paul Brook]

On Sunday 15 April 2007 14:46, Nigel Horne wrote:
> Let me approach this in a different way in the hope that I'll get an answer
> to my question: will Qemu run a 286 guest O/S?

Yes.

Paul

Re: [Qemu-devel] 16-bit (and 8-bit) emulation

[Nigel Horne]

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Paul Brook wrote:
> On Sunday 15 April 2007 14:46, Nigel Horne wrote:
>> Let me approach this in a different way in the hope that I'll get an answer
>> to my question: will Qemu run a 286 guest O/S?
> 
> Yes.

Good.

Followup question, if the guest O/S is multi-architecture, will it run in 386
mode (which I don't want for this particular scenario) or can I force it to only "see" a 286
so that it doesn't boot up in 386 mode?

> 
> Paul

-Nigel


-- 
Nigel Horne. Arranger, Adjudicator, Band Trainer, Composer, Tutor, Typesetter.
NJH Music, Barnsley, UK.  ICQ#20252325
njh@bandsman.co.uk http://www.bandsman.co.uk

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Re: [Qemu-devel] 16-bit (and 8-bit) emulation

[Natalia Portillo]

Yes but...

Currently no protected mode 286 guest OS runs under qemu.

El dom, 15-04-2007 a las 14:46 +0100, Nigel Horne escribió:
> Let me approach this in a different way in the hope that I'll get an answer to my
> question: will Qemu run a 286 guest O/S?
> 
> -Nige

Re: [Qemu-devel] 16-bit (and 8-bit) emulation

[Derek Fawcus]

On Sun, Apr 15, 2007 at 08:55:17PM +0100, Natalia Portillo wrote:
> Yes but...
> 
> Currently no protected mode 286 guest OS runs under qemu.

Windows 3.1 Standard mode?  (Delete / Rename KRNL386.EXE)

DF

> 
> El dom, 15-04-2007 a las 14:46 +0100, Nigel Horne escribió:
> > Let me approach this in a different way in the hope that I'll get an answer to my
> > question: will Qemu run a 286 guest O/S?
> > 
> > -Nige
> 

Re: [Qemu-devel] 16-bit (and 8-bit) emulation

[Natalia Portillo]

Windows 3.1 is not an OS.

And there is no Windows for 286 protected mode.

There is OS/2 and UNIXen but none works (OS/2 2.0 and later UNIXen works
but they are 386 protected mode)

El mar, 17-04-2007 a las 00:35 +0100, Derek Fawcus escribió:
> On Sun, Apr 15, 2007 at 08:55:17PM +0100, Natalia Portillo wrote:
> > Yes but...
> > 
> > Currently no protected mode 286 guest OS runs under qemu.
> 
> Windows 3.1 Standard mode?  (Delete / Rename KRNL386.EXE)
> 
> DF
> 
> > 
> > El dom, 15-04-2007 a las 14:46 +0100, Nigel Horne escribió:
> > > Let me approach this in a different way in the hope that I'll get an answer to my
> > > question: will Qemu run a 286 guest O/S?
> > > 
> > > -Nige
> > 
> 
> 
> 

Re: [Qemu-devel] 16-bit (and 8-bit) emulation

[Andreas Schwab]

Nigel Horne <njh@bandsman.co.uk> writes:

> I can't remember now what sizeof(int) and sizeof(char *) were on m68k machines.

It depends.  Try -mshort.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
PGP key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: [Qemu-devel] 16-bit (and 8-bit) emulation

[Nigel Horne]

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Andreas Schwab wrote:
> Nigel Horne <njh@bandsman.co.uk> writes:
> 
>> I can't remember now what sizeof(int) and sizeof(char *) were on m68k machines.
> 
> It depends.  Try -mshort.

That's not much help, I'm sorry to say, because you need an m68k machine to use
it on, and there's no qemu-system-m68k, only a qemu-m68k.

> 
> Andreas.
> 


-- 
Nigel Horne. Arranger, Adjudicator, Band Trainer, Composer, Tutor, Typesetter.
NJH Music, Barnsley, UK.  ICQ#20252325
njh@bandsman.co.uk http://www.bandsman.co.uk

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Re: [Qemu-devel] 16-bit (and 8-bit) emulation

[Andreas Schwab]

Nigel Horne <njh@bandsman.co.uk> writes:

> Andreas Schwab wrote:
>> Nigel Horne <njh@bandsman.co.uk> writes:
>>
>>> I can't remember now what sizeof(int) and sizeof(char *) were on m68k machines.
>>
>> It depends.  Try -mshort.
>
> That's not much help, I'm sorry to say, because you need an m68k machine to use
> it on, and there's no qemu-system-m68k, only a qemu-m68k.

Why do you need a full emulation?  The choice of sizeof(int) has no
influence on the cpu.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
PGP key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: [Qemu-devel] 16-bit (and 8-bit) emulation

[Todd T. Fries]

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[-- Attachment #1: Type: text/plain; charset=unknown-8bit, Size: 1906 bytes --]

todd@cloud/p1 ~/src/c/todd/test¦100$ ./sizeof
sizeof(char) = 1
sizeof(short) = 2
sizeof(int) = 4
sizeof(char *) = 4
sizeof(long) = 4
sizeof(long long) = 8
todd@cloud/p1 ~/src/c/todd/test¦101$ uname -a
OpenBSD cloud.fries.net 4.1 GENERIC#7 mac68k
todd@cloud/p1 ~/src/c/todd/test¦102$ 

FWIW.
-- 
Todd Fries .. todd@fries.net

 _____________________________________________
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Penned by Nigel Horne on 20070415 13:08.57, we have:
| Stuart Brady wrote:
| >On Sun, Apr 15, 2007 at 11:08:56AM +0100, Nigel Horne wrote:
| >>Can qemu emulate 16-bit machines (286?)?
| >
| >None that I'm aware of.  Is there any particular need for 286 emulation?
| 
| To test my code on machines where sizeof(int) == sizeof(short), and
| sizeof(int) != sizeof(long).
| 
| >OTOH, it might be interesting to see some m68k system emulation.
| 
| I can't remember now what sizeof(int) and sizeof(char *) were on m68k 
| machines.
| 
| -Nigel
| 
| -- 
| Nigel Horne. Arranger, Adjudicator, Band Trainer, Composer, Tutor, 
| Typesetter.
| NJH Music, Barnsley, UK.  ICQ#20252325
| njh@bandsman.co.uk http://www.bandsman.co.uk

| begin:vcard
| fn:Nigel Horne
| n:Horne;Nigel
| org:NJH Music
| email;internet:njh@bandsman.co.uk
| tel;fax:+44 870 705 9334
| note:Skype: nigelhorne
| x-mozilla-html:FALSE
| version:2.1
| end:vcard
| 

Re: [Qemu-devel] Report

[Thiemo Seufer]

Nigel Horne wrote:
> Folks,
> 
> Thanks for qemu. I thought you may like to know that from a Linux x86 host
> I have 3 linux guests: sparc, arm and mips. The first 2 work a treat, the
> mips keeps core dumping in libc6 when called from Perl, I don't know if
> the problem lies in libc6, perl or qemu.

I assume you are using full system emulation for mips. I currently see
some instability when running specific perl scripts which is apparently
triggered by the FPU emulator in the Linux/MIPS kernel. As a workaround,
use -cpu 24Kf.


Thiemo

Re: [Qemu-devel] Report

[Nigel Horne]

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Thiemo Seufer wrote:
> Nigel Horne wrote:
>> Folks,
>>
>> Thanks for qemu. I thought you may like to know that from a Linux x86 host
>> I have 3 linux guests: sparc, arm and mips. The first 2 work a treat, the
>> mips keeps core dumping in libc6 when called from Perl, I don't know if
>> the problem lies in libc6, perl or qemu.
> 
> I assume you are using full system emulation for mips. I currently see
> some instability when running specific perl scripts which is apparently
> triggered by the FPU emulator in the Linux/MIPS kernel. As a workaround,
> use -cpu 24Kf.

Yes, that works a treat, thanks. I wonder if it's worth reporting as a kernel
bug.

> Thiemo

-Nigel

-- 
Nigel Horne. Arranger, Adjudicator, Band Trainer, Composer, Tutor, Typesetter.
NJH Music, Barnsley, UK.  ICQ#20252325
njh@bandsman.co.uk http://www.bandsman.co.uk

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Re: [Qemu-devel] Report

[Thiemo Seufer]

Nigel Horne wrote:
> Thiemo Seufer wrote:
> >Nigel Horne wrote:
> >>Folks,
> >>
> >>Thanks for qemu. I thought you may like to know that from a Linux x86 host
> >>I have 3 linux guests: sparc, arm and mips. The first 2 work a treat, the
> >>mips keeps core dumping in libc6 when called from Perl, I don't know if
> >>the problem lies in libc6, perl or qemu.
> >
> >I assume you are using full system emulation for mips. I currently see
> >some instability when running specific perl scripts which is apparently
> >triggered by the FPU emulator in the Linux/MIPS kernel. As a workaround,
> >use -cpu 24Kf.
> 
> Yes, that works a treat, thanks. I wonder if it's worth reporting as a 
> kernel bug.

It is a Qemu bug. On real hardware it works fine.


Thiemo