Re: [Qemu-devel] Re: Missing singlestep for already-translated code?

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

Alexander Graf wrote:
> On 13.04.2010, at 15:36, Jan Kiszka wrote:
> 
>> Jun Koi wrote:
>>> Hi,
>>>
>>> I am looking into the singlestep command in monitor interface, and it
>>> seems that we only take into account the singlestep flag when we are
>>> translating code.
>>> So for the already-translated code, we will miss singlestep?
>> This feature is broken. For TCG, it should at least flush the
>> translation buffer, and for KVM it has to enable single-stepping in the
>> kernel. That's what happens automatically when you call cpu_single_step.
>> I guess 'singlestep' wants to be somehow orthogonal to this. But this is
>> the wrong approach.
>>
>> Does anyone actually used this feature or still does so? It looks fairly
>> redundant to me, kind of a poor-man's gdb front-end as part of the
>> monitor console.
> 
> Not sure what it does, but I use -singlestep quite a lot to get register dumps for instructions when using -d cpu.

Ah, "singlestep" is not about stopping the VM after each instruction but
about limiting the TB length to a single instruction. Badly named and
poorly documented.

In that case, the dynamic switch should already be fine by adding a
tb_flush() on enable. Still, someone should also patch at least the docs.

Jan

-- 
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux