Re: [Qemu-devel] Guest to Qemu communication channel + static instrumentation

[Anthony Liguori <anthony@codemonkey.ws>]

On 07/08/2010 12:49 PM, Lluís wrote:
> Hi there.
>
> I'm porting into qemu some code I had for bochs. For this purpose, the first
> part is a backdoor communication channel, such that code in the guest will be
> able to directly communicate with qemu in a pre-defined manner (namely, the
> decode of an illegal instruction).
>    

At least for x86, there is a well defined instruction for these purposes 
(vmcall and vmmcall respectively).  I think qemu implementing 
vmcall/vmmcall emulation for TCG is not a bad idea.

> Right now, this comes with a '--with-backdoor=PATH' flag in the configure
> script, which lets the user activate the communication channel, and make qemu
> compile all '.c' files in PATH as target code.
>
> In those files, the user can place any code, plus backdoor callbacks (these are
> a must), which are free to interact with any other piece of code in qemu.
>
> Are you interested on merging this kind of functionality?
>
> The only reason for this is to control the behaviour of the other piece of code
> I'm working on (which I would very much like to integrate into qemu).
>
> This other piece is a set of static instrumentation points using macros that the
> user can re-define at compile time.
>
> For an example of how it would look like:
>      http://bochs.sourceforge.net/cgi-bin/lxr/source/instrument/
>    

It's not immediately clear to me how this would map to TCG so I'm 
unclear about it's utility.

Regards,

Anthony Liguori

> Read you,
>       Lluis
>
>