Re: [Qemu-devel] [RFC] ARMCPU: Halting a CPU from Device Land

[Peter Crosthwaite]

On Mon, Jun 18, 2012 at 8:07 PM, Andreas Färber <address@hidden> wrote:
> Hi Peter,
>
> Am 18.06.2012 09:22, schrieb Peter Crosthwaite:
>> Hi Andreas,
>>
>> For the Xilinx Zynq platform, we need to be able to halt a CPU from a
>> device (the zynq_slcr). E.G, if I write a 1 to a register bit in my
>> device, then that device effects a halt of a CPU. Looking at the QOM
>> stuff the API for a CPU is (include/qemu/cpu.h):
>>
>> typedef struct CPUClass {
>>     /*< private >*/
>>     ObjectClass parent_class;
>>     /*< public >*/
>>
>>     void (*reset)(CPUState *cpu);
>> } CPUClass;
>>
>> The only API function is to reset a CPU. Thats means that if I link up
>> my CPU to my device the only thing it can do is reset the CPU? Are
>> there plans to extend this API to include some common functions such
>> as halting and resuming etc? How hard is this to do in a generic (non
>> ARM) way?
>>
>> Peter,
>>
>> Can it be done is an ARM specific way? Is there a one line killer to
>> halt an ARM cpu that we could add the to ARMCPU API?
>
> I'll answer both:
>
> There's the QOM CPUState part 4 series on the list that sequentially
> moves more and more fields into CPUState. So far the good news. The bad
> news is that merging the halted field movement - despite on the list -
> depends on refactorings of the TLB that I haven't gotten around to yet.
> (Still caught up in packaging v1.1.)
>
> The ARM-specific way is to cast your CPUState with ARM_CPU(), assuming
> your Zynq device is compiled per target like most ARM devices currently
> are, then you can access ->env (CPUARMState), which still has the halted
> field.

Hi Andreas,

So whats the sensible course of action implementation wise? #include
cpu.h in my device, cast to ARM_CPU(), ->env->halted = 1, with a /*
FIXME */ ?? Cos this approach seems hacky so is it really acceptable
if I were to create a series that does this today?

Regards,
Peter

>
> Cheers,
> Andreas
>
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