Re: [Qemu-devel] QEMU as ISS (Instruction Set Simulator)

[=?gb18030?B?TGlibyBaaG91?= <zhlb29@foxmail.com>]

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Hi Aleksandar,


Thank you for the link to Loongson2F documentation. It has been very useful:)


I have spent several days immersing myself in the source code, now I think I have a more solid understanding about it. Just like Loongson Multimedia Instructions, I need to implement some sort of complex vector instructions, and I need to write some helper functions (e.g. my_helper.c).


The QEMU wiki website has very thorough explanation on TCG, but I haven't found any explanation on the port-specific helpers. Is there any documentation on how the helper functions are generated? I think now I *might* know how to write a working helper function, but I just don't know how it works.


Cheers,
Libo









------------------ Original message ------------------
From: "Aleksandar Markovic"; 
Sendtime: Thursday, Aug 22, 2019 6:53 PM
To: "Libo Zhou"; 
Cc: "qemu-devel"; 
Subject: Re: [Qemu-devel] QEMU as ISS (Instruction Set Simulator)



On Thu, Aug 22, 2019 at 12:24 PM Á¢ <zhlb29@foxmail.com> wrote:

> Hi Aleksandar,
>
> Thank you very much for your patient explanation in the previous post. And
> thank you for checking.
> Your and Peter's replies in the previous post certainly helped a lot. I am
> now looking at a git commit 7 years ago (
> bd277fa1966bc400f1b411f868f39125cda0c403), it was a Loongson Multimedia
> Instruction implementation done my Richard Henderson.
>

Cool, that commit is a very good staring point - it is definitely not too
simple, and it is not too complex either. And you can discover several
different concepts in the process of exploring the change.

Documentation on instruction set extension related to the commit (found by
Google):
https://files.somniafabularum.com/loongson/docs/Loongson2FUserGuide.pdf

Be persistent, take your time, study the details and handling of individual
instructions, and, of course, let us know if you encounter some major
obstacles or thorny dilemmas.

Yours,
Aleksandar


> I think what he did is exactly what I want to do now. I got a vague view
> of the big picture, but I need more time to figure out the details. I will
> certainly ask more questions about this later, but before that I need to
> look at some other parts of the source code:) Again thank you for checking!
>
> Cheers,
> Libo
>
>
> ------------------ Original message ------------------
> *From:* "Aleksandar Markovic";
> *Sendtime:* Thursday, Aug 22, 2019 4:23 PM
> *To:* "Á¢";
> *Cc:* "qemu-devel";
> *Subject:* Re: [Qemu-devel] QEMU as ISS (Instruction Set Simulator)
>
> On Tue, Aug 20, 2019 at 12:12 PM Á¢ <zhlb29@foxmail.com> wrote:
>
> > I am working on a project that requires me to modify the ISA of the MIPS
> > target.
>
>
> L.,
>
> How is it going?
>
> Aleksandar
>
>
>
> > I have been staring at the source code for about a week, but found it
> > really difficult due to me being a young rookie and the sparse comments.
> > Specifically, I need to extend MIPS, by adding some new instructions and
> > new CPU registers to the current architecture, and that sounds really
> easy.
> > I think the place for me to look at should be at the directory
> > ${qemu_root}/target/mips/. With a MIPS Instruction Set Manual Release 6
> > handy, I have difficulty finding the source code where the ISA resides.
> Is
> > it in op_helper.c? Or translate.c? Any guidance would be really
> > appreciated. Thank you very much in advance.
> >
> >
> > Cheers,
> > L.
>