[Qemu-devel] Re: [PATCH] optionally specify vm stop message

[Jan Kiszka <jan.kiszka@siemens.com>]

Jan Kiszka wrote:
> Anthony Liguori wrote:
>> Jan Kiszka wrote:
>>> Anthony Liguori wrote:
>>>  
>>>>>  Also non zero reasons a handled differently by vm_stop. Don't know
>>>>> why.
>>>>>         
>>>> It's an ugly hack for gdbstub.  It notifies gdb when a breakpoint
>>>> occurs.  We have far too many state tracking mechanisms.  Anyway, gdb
>>>> can pass something like VM_STOP_BP and that can be used to trigger the
>>>> callback.
>>>>     
>>> It's not only used for breakpoints but any stop condition that should be
>>> reported to the gdb frontend (so far: EXCP_DEBUG and EXCP_INTERRUPT).
>>> Not sure, though, how to deal with ENOSPC - it's not a guest fault, it's
>>> a host problem. From that POV, gdb should not receive it.
>>>   
>> We already have a vm_change_state_handler that is invoked whenever a
>> guest starts running or stops running.  gdb should be able to use that
>> and look at env->exception_index, no?
> 
> I don't think env->exception_index is set when you issue "stop" from the
> monitor, e.g. Moreover, that would be an ugly (out-of-band) API as well.
> 

The point is that vm_stop can be issued from any context, not just from
a vcpu. So there may be no env channel at this point.

Jan

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