Re: [Qemu-devel] Release of COREMU, a scalable and portable full-system emulator

[Chen Yufei]

On 2010-7-22, at 上午1:04, Stefan Weil wrote:

> Am 21.07.2010 09:03, schrieb Chen Yufei:
>> On 2010-7-21, at 上午5:43, Blue Swirl wrote:
>> 
>>   
>>> On Sat, Jul 17, 2010 at 10:27 AM, Chen Yufei<address@hidden>  wrote:
>>>     
>>>> We are pleased to announce COREMU, which is a "multicore-on-multicore" 
>>>> full-system emulator built on Qemu. (Simply speaking, we made Qemu 
>>>> parallel.)
>>>> 
>>>> The project web page is located at:
>>>> http://ppi.fudan.edu.cn/coremu
>>>> 
>>>> You can also download the source code, images for playing on sourceforge
>>>> http://sf.net/p/coremu
>>>> 
>>>> COREMU is composed of
>>>> 1. a parallel emulation library
>>>> 2. a set of patches to qemu
>>>> (We worked on the master branch, commit 
>>>> 54d7cf136f040713095cbc064f62d753bff6f9d2)
>>>> 
>>>> It currently supports full-system emulation of x64 and ARM MPcore 
>>>> platforms.
>>>> 
>>>> By leveraging the underlying multicore resources, it can emulate up to 255 
>>>> cores running commodity operating systems (even on a 4-core machine).
>>>> 
>>>> Enjoy,
>>>>       
>>> Nice work. Do you plan to submit the improvements back to upstream QEMU?
>>>     
>> It would be great if we can submit our code to QEMU, but we do not know the 
>> process.
>> Would you please give us some instructions?
>> 
>> --
>> Best regards,
>> Chen Yufei
>>   
> 
> Some hints can be found here:
> http://wiki.qemu.org/Contribute/StartHere
> 
> Kind regards,
> Stefan Weil

The patch is in the attachment, produced with command
git diff 54d7cf136f040713095cbc064f62d753bff6f9d2

In order to separate what need to be done to make QEMU parallel, we created a 
separate library, and the patched QEMU need to be compiled and linked with that 
library. To submit our enhancement to QEMU, maybe we need to incorporate this 
library into QEMU. I don't know what would be the best solution.

Our approach to make QEMU parallel can be found at 
http://ppi.fudan.edu.cn/coremu

I will give a short summary here:

1. Each emulated core thread runs a separate binary translator engine and has 
private code cache. We marked some variables in TCG as thread local. We also 
modified the TB invalidation mechanism.

2. Each core has a queue holding pending interrupts. The COREMU library 
provides this queue, and interrupt notification is done by sending realtime 
signals to the emulated core thread.

3. Atomic instruction emulation has to be modified for parallel emulation. We 
use lightweight memory transaction which requires only compare-and-swap 
instruction to emulate atomic instruction.

4. Some code in the original QEMU may cause data race bug after we make it 
parallel. We fixed these problems.

patch-to-54d7cf136f040713095cbc064f62d753bff6f9d2
Description: Binary data

--
Best regards,
Chen Yufei