Re: [Qemu-devel] [PATCH RFC qom-cpu 39/41] target-xtensa: Introduce XtensaCPU subclasses

["Andreas Färber" <afaerber@suse.de>]

Am 06.07.2013 20:39, schrieb Max Filippov:
> On Sat, Jul 6, 2013 at 10:01 PM, Max Filippov <jcmvbkbc@gmail.com> wrote:
>> On Sat, Jul 6, 2013 at 4:55 PM, Andreas Färber <afaerber@suse.de> wrote:
>>> Am 29.06.2013 22:01, schrieb Andreas Färber:
>>>> Register a CPU type per core registered. Save the XtensaConfig in
>>>> XtensaCPUClass instead of CPUXtensaState.
>>>>
>>>> Prepares for storing per-class GDB register count.
>>>>
>>>> Signed-off-by: Andreas Färber <afaerber@suse.de>
>>>
>>> Ping! Can you ack? (It did not seem to break your test image.)
>>
>> Hi Andreas,
>>
>> I tried make check -C tests/tcg/xtensa with the branch you recommended
>> and it segfaults on elf loading
> 
> ...and maybe a stupid question, but why moving configuration pointer away
> from env and then changing every place that used to access it?

Xtensa is the only target trying to implicitly access an "env" variable
through a macro to obtain the number of registers for gdbstub. That's
what I'm trying to fix with 40/41 in order to get rid of the #ifdeffery.

The number of registers is not accessed by TCG, so it could go into
XtensaCPU instead of CPUXtensaState.
Further it does not change during vCPU runtime, so it no longer belongs
in CPUXtensaState nor XtensaCPU but in XtensaCPUClass, which is shared
among CPU cores and can be accessed statically.
However we only had one XtensaCPUClass but multiple XtensaConfigs.
Therefore this patch registers one XtensaCPUClass per XtensaConfig.

You might remember that I once tried to place the XtensaConfig fields
directly into XtensaCPUClass but that didn't work out nicely back then.
This is by comparison a slim/minimal conversion to subclasses, leaving
XtensaConfig and your custom registration mechanisms in place. Cleaning
that up to use type_init() and type_register_static() in the respective
source files and changing -cpu ? to iterate QOM types would be a nice
follow-up, but not needed for this gdbstub refactoring series.

Another background is that I'm trying to get rid of cpu_init() and
anything that blocks using -device or device_add with QOM CPUs.

Regards,
Andreas

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