Re: Getting qemu plugins working on windows

[Richard Henderson]

On 10/30/23 09:48, Greg Manning wrote:
> Hello,
>
> Currently, qemu plugin support only works in Linux and I would like to get qemu 
> plugins working on
> Windows. I have had some success experimenting with this locally (based on some 
> previous work by
> Yonggang Luo, see below), but would like to gauge opinion before I commit to 
> suggesting a solution.
>
> The overall structure of how plugins work is this:
>
> 1. qemu executable loads plugin.so.
> 2. plugin.so defines a function qemu_plugin_install, which qemu looks up, and 
> calls.
> during that function call plugin.so might call some of the qemu_plugin_* 
> functions that the host
> executable has implementations of. plugin.so is compiled with unresolved 
> references to these functions,
> and they get linked up at dll load time.
>
> Windows doesn't let you do such on-the-fly load time linking. You need a dll 
> import library, which is
> specific to a particular host executable. The qemu project, however, has many 
> executables, any
> of which might want to load a given plugin.
>
> Possible ways to get things working on Windows:
>
> 1. Make the dll import library. Possibly refactor the qemu plugin code into a 
> single qemu_plugin.{so,dll},
>     and then make the import library for that. I don't fully understand this 
> system, and I'm still concerned
>     it would be fragile (if qemu is recompiled, do I need to recompile all my 
> plugins against the new
>     version of the import library?)

As we work toward a single qemu executable, I expect that we will need to build most of 
qemu as a dll, and then you'd have exactly the image against which plugins could be linked.

This is probably still a couple of releases away from daylight, but I wouldn't want too 
much work to be done on an alternate method for Windows in the meantime.


r~