get backtrace of KVM VM from host

[Justin Cinkelj <justin dot cinkelj at xlab dot si>]

(crossposting from KVM maillist)

Hi

Is it possible to get stack backtrace into KVM VM from the host side? So 
if I run './stack -p PID' (stack from elfutilfs 
https://sourceware.org/elfutils/), I get backtrace of some process. I 
would like to do the same for VM. I can assume VM will run only a kernel 
(a unikernel, like OSv or IncludeOS), so most/all debug symbols will be 
there in a single file, and at least IncludeOS doesnt load any code 
beside its own kernel.

I did notice KVM_GET_REGS and KVM_SET_MEMORY_REGION, and at least for 
trivial examples (like https://github.com/dpw/kvm-hello-world) this 
provides enough information to track which code was loaded into VM, 
observe current stack content and registers. I can only guess much more 
work is required to get similar result with qemu-kvm. Hence I'm asking 
if this is already implemented.

Thank you,
Justin