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

[fabrice . bellard]

Quoting Bradon Kanyid <address@hidden>:

> 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.