Re: [Qemu-devel] [RFC] TCG unit testing

[Lei Li <lilei@linux.vnet.ibm.com>]

On 08/24/2013 04:42 AM, Stefan Weil wrote:
> Am 23.08.2013 21:47, schrieb Richard Henderson:
>> I've been thinking for a while about how to reliably test TCG backends, and
>> maybe how to do regression testing on them.  Having to begin the test from a
>> guest binary, especially considering the vast cross-compilation problem, is
>> pretty much a non-starter.
>>
>> I've been thinking of a truly stripped down target for the purpose, with a
>> special-purpose machine loop and main to go with it.  I.e. avoid vl.c.
>>
>> My current idea is that the test file consists of 3 sections: guest memory
>> layout, raw TBs, and expected results.  Perhaps best explained with some examples:
>>
>> (1a) I've split up this test into two TBs to prevent some constant folding.
>> (1b) The guest machine should have enough registers to make it easy to perform
>> lots of tests at once.  Even better if we can avoid the complication of memory.
>>
> [...]
>> Thoughts?  Anything that we ought to be testing that I haven't thought of here,
>> and that this sort of structure couldn't support?
>>
>> It may be some time before I can progress this enough to usefulness, but I
>> wanted to get this written down while it is fresh in my head.
>>
>>
>> r~
> Since the addition of the TCG interpreter backend, there exist two
> backends for each supported host. It is possible to run user code
> with well defined instruction order (no asynchronous events like
> interrupts) with both backends and to compare the execution
> flow. I did that while developing TCI. The process can be reversed:
> TCI could be used as reference to test any other backend.
>
> Another approach for testing TCG backends might work like this:
>
> Modifying QEMU so that it is possible to feed the TCG backend
> with single TCG opcodes would allow testing some part of the
> processing chain:
>
> target opcodes -> tcg opcodes -> host opcodes
>                    <------------------------->

Really nice if we could support this!

>
> Regards,
> Stefan
>
>


-- 
Lei