Re: Debugging multi-threaded TCG for aarch64 emulation (stalled vCPU)

[Alex Bennée]

Jesus Sanchez-Palencia
<forgerbr-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> writes:

> Hi there,
>
> I'm investigating an intermittent issue where one of the vCPUs is
> stalled during the MTCG main loop, so I'm sampling all vCPUs state to
> rootcause the issue.

How is it stalled? Is it busy looping running guest code or has it
exited the run loop?

>
> Is there a way to print which instruction a TCG thread is currently 
> emulating? I have access to all pointers to CPUState, TranslationBlock, etc. 
> lookup_symbol() doesn't return anything and I'm not
> seeing any other obvious options.

The hammer approach is to run with -d exec,cpu

which will dump the CPU state each time the code enters the run loop.

>
> I'd appreciate some guidance here.

With my developer hat on I would attach gdb to QEMU itself and run:

  thread apply bt all

and start poking around from there. If the thread in question is not
running actual guest code then the state of CPUState will be valid.

>
> Thanks.
>

-- 
Alex Bennée