Re: [Xen-devel] VMI: singlestep event not received

[Tamas K Lengyel <tamas.k.lengyel@xxxxxxxxx>]

> > I'm not entirely sure what you mean here (and perhaps that's a
> > discussion to be moved to the LibVMI issues page). If you already have
> > an event registered for singlestepping why would you want to disable
> > it just to re-enable it? If it's because you just have the handler
> > registered without MTF actually active, that's specifically made for
> > the situation where turn on/off MTF using the VM_EVENT_RESPONSE_FLAG.
>
> The reason is because i needed an on-demand activation of MTF, without being 
> in an event callback.
>
> Let's say my GDB client asks me to do one singlestep.
> I will need to register a new singlestep event, enabled, listen
> one event and then return.
>
> The problem is that I already have my singlestep event for breakpoint 
> recoiling purposes which is registered.
>
> That's the reason I'm unregistering this recoil singlestep event and 
> reregistering it afterwards, because I can't "reuse" it:
> https://github.com/Wenzel/pyvmidbg/blob/master/vmidbg/breakpoint.py#L79

Yea, that seems suboptimal. Provided there is already a
vmi_stop_single_step_vcpu function in LibVMI which just removes the
MTF from a given vCPU, I would recommend replacing that function with
a generic one that you can use to both enable/disable MTF on a
per-vCPU base.

>
> I actually discussed it with you here:
> https://github.com/libvmi/libvmi/issues/665

I see I actually made a very similar recommendation in that discussion
then what I just described above ;)

Cheers,
Tamas

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