No offense intended toward Ingo, but there really isn't a huge insurmountable technical challenge here. Both Avi and Daniel have suggested perfectly valid technology fixes (that just happen to not be exactly what Ingo asked for, but are not invalid either):
*). A symbol server in guests exporting the data you want/need.
*). libguestfs if you really want to violate a running guest.
Personally, I like perf, but it is just a tool. It's a nice tool and it might be nice to poke at a running guest in some situations (I consider already that there is too much coupling here for safety and would rather the kernel not be doing that directly) but there are plenty of ways to get at the required data and process it without merging whole other projects into the kernel or requiring the kernel to re-implement libvirt features.
I'd rather the kernel had nice stable versioned interfaces with some tools in tree, and others out of tree, and that that not be a big deal. The issue of developers not paying attention between userspace and kernel is a cultural divide that needs fixing - sites like LWN do a good job at educating about ongoing work - and that can be done by simply poking at something of interest without changing any development process.