Hi,

On Wed, Sep 3, 2025 at 6:56 PM Sahil Khan <[email protected]> wrote:
>
> Hii Doug, Thanks for the reply.
> I am aware about the stop mode debugging of kgdb/kdb. I have worked with 
> kgdb/kdb on
> 1. Qemu hypervisor.
> 2. VMware esxi/vcentre.
>
> Now, I know that on Qemu ( if you have access to the machine on which it is 
> running) Virtual machine serial ports are generally mapped to some tty device 
> on the host machine. Data can be relayed by socat(ing) the ttys of the 2 
> virtual machines( target and debugger). But the vm serial port to tty mapping 
> is not persistent on reboots, tty is reassigned most of the time.

The problem of the tty being reassigned feels like a very solvable problem.


> Now for VMware based virtual machines, we do not have the access to the 
> machine running the hypervisor. So the above method generally does not work. 
> Things are made more difficult when the serial device support for virtual 
> machines is disabled by the hypervisor.

Figuring out how to get access to this serial port also feels like a
solvable problem, but perhaps there are politics involved so who
knows...


> What I think should be considered for kgdb/kdb is :
> 1. Provide nework debugging support similar to serial device based debugging.

If you feel like you can write patches to make this work in a way
that's not too hacky then feel free to post them. This feels like it
would be quite difficult, though I suppose if you're trying to
constrain yourself to some network device that's exposed by some VM
then maybe it's not impossible. Almost certainly this would be
impossible for 99% of network devices. No way are you going to get any
large percentage of network devices to work under a stop mode
debugger.


> 2. Allow user to choose the frontend b/d kdb and kgdb, since kdb is the 
> default from unless we want to switch but that switcj requires kdb prompt 
> running.

I'm not quite sure what the big deal is here. If you just start GDB
when the kdb prompt is up then it auto-transitions over, doesn't it? I
seem to remember there are a bunch of options around this too. ...but
if what's there doesn't work for you then feel free to submit a patch.
If the patch looks good/useful then it can be landed.

-Doug


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