[Qemu-devel] How difficult to strip this down?

[Qemu-devel] How difficult to strip this down?

[Bradon Kanyid]

Hi,

I was wondering about how difficult it would be to strip down the cpu 
emulation to a simpler form? I need a x86 emulator that will work on an 
ARM9, but I don't need a lot of the extras that are included in your source. 
Really, I only need 80186 cpu emulation, and very little else. I was 
wondering if hacking out all the rest would be easy, or is this just a waste 
of my time? Also, you didn't post any benchmarks for the ARM with your 
recent benchmarks. My current emulation is probably about 20 arm 
instructions to 1 x86 instruction (I'm using a crappy MAME cpu core), and it 
appears for other cpus like the PPC that you get a 10-1 ratio. If I could 
get something like that, that'd be great. Anyways, this project looks great, 
and I'd like to be able to use it, but if it's something totally different 
from what I'm looking for, I'd like to know before I waste my time. Thanks

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Re: [Qemu-devel] How difficult to strip this down?

[Herbert Pötzl]

On Tue, Jul 15, 2003 at 03:58:56PM -0700, Bradon Kanyid wrote:
> Hi,
> 
> I was wondering about how difficult it would be to strip down the cpu 
> emulation to a simpler form? I need a x86 emulator that will work on an 
> ARM9, but I don't need a lot of the extras that are included in your 
> source. Really, I only need 80186 cpu emulation, and very little else. I 
> was wondering if hacking out all the rest would be easy, or is this just a 
> waste of my time? Also, you didn't post any benchmarks for the ARM with 
> your recent benchmarks. My current emulation is probably about 20 arm 
> instructions to 1 x86 instruction (I'm using a crappy MAME cpu core), and 
> it appears for other cpus like the PPC that you get a 10-1 ratio. If I 
> could get something like that, that'd be great. Anyways, this project looks 
> great, and I'd like to be able to use it, but if it's something totally 
> different from what I'm looking for, I'd like to know before I waste my 
> time. Thanks

maybe you should also have a look at bintrans
a dynamic binary translator which uses a generalized
machine description to go from one architecture to
the other ...

although it does not support arm yet, it is easy to
adapt/extend and very fast ...

best,
Herbert

Re: [Qemu-devel] How difficult to strip this down?

[fabrice.bellard]

Quoting Bradon Kanyid <rattboi24@hotmail.com>:

> Hi,
> 
> I was wondering about how difficult it would be to strip down the cpu 
> emulation to a simpler form? I need a x86 emulator that will work on an 
> ARM9, but I don't need a lot of the extras that are included in your source.
> 
> Really, I only need 80186 cpu emulation, and very little else. I was 
> wondering if hacking out all the rest would be easy, or is this just a waste
> 
> of my time? Also, you didn't post any benchmarks for the ARM with your 
> recent benchmarks. My current emulation is probably about 20 arm 
> instructions to 1 x86 instruction (I'm using a crappy MAME cpu core), and it
> 
> appears for other cpus like the PPC that you get a 10-1 ratio. If I could 
> get something like that, that'd be great. Anyways, this project looks great,
> 
> and I'd like to be able to use it, but if it's something totally different 
> from what I'm looking for, I'd like to know before I waste my time. Thanks

With QEMU/arm, it should be possible to be even faster if you handle unaligned
accesses with a trap (it is not done currently in QEMU as I was not permitted to
change the unaligned access mode on the host I was using). Of course you get a
slowdown if the code does too many unaligned accesses.

I don't think it is worth stripping the emulation to a simpler form : the code
is already quite small. Did you try using libqemu.a as is ? A patch you may need
is the handling of real mode (QEMU only handles protected and vm86 modes yet,
but real mode would be very easy to add).

Fabrice.