Re: [Xen-devel] [PATCH 3/3] xen/arm: vpsci: Move PSCI function dispatching from vsmc.c to vpsci.c

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 30 January 2018 at 19:35, Volodymyr Babchuk
<volodymyr_babchuk@xxxxxxxx> wrote:
>
>
> On 30.01.18 20:44, Julien Grall wrote:
>>
>>
>>
>> On 30/01/18 18:28, Volodymyr Babchuk wrote:
>>>
>>> Hi Julien,
>>>
>>> On 30.01.18 20:01, Julien Grall wrote:
>>>>
>>>>
>>>>
>>>> On 26/01/18 18:27, Volodymyr Babchuk wrote:
>>>>>
>>>>> Hi,
>>>>
>>>>
>>>> Hi Volodymyr,
>>>>
>>>>> On 26.01.18 20:15, Julien Grall wrote:
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> On 26/01/18 18:09, Volodymyr Babchuk wrote:
>>>>>>>
>>>>>>> On 24.01.18 20:34, Julien Grall wrote:
>>>>>>>>
>>>>>>>> -    case PSCI_0_2_FN32(AFFINITY_INFO):
>>>>>>>> -    case PSCI_0_2_FN64(AFFINITY_INFO):
>>>>>>>> +    switch ( fid )
>>>>>>>>       {
>>>>>>>> -        register_t taff = PSCI_ARG(regs, 1);
>>>>>>>> -        uint32_t laff = PSCI_ARG32(regs, 2);
>>>>>>>> -
>>>>>>>> -        perfc_incr(vpsci_cpu_affinity_info);
>>>>>>>> -        PSCI_SET_RESULT(regs, do_psci_0_2_affinity_info(taff,
>>>>>>>> laff));
>>>>>>>> -        return true;
>>>>>>>> -    }
>>>>>>>> -
>>>>>>>>       case ARM_SMCCC_FUNC_CALL_COUNT(STANDARD):
>>>>>>>>           return fill_function_call_count(regs,
>>>>>>>> SSSC_SMCCC_FUNCTION_COUNT);
>>>>>>>
>>>>>>> Now definition SSSC_SMCCC_FUNCTION_COUNT depends on code in vscpi.c.
>>>>>>> Maybe it is time to introduce function get_psci_0_2_fn_count() and
>>>>>>> use it there, what do you think?
>>>>>>
>>>>>>
>>>>>> Definitely not a function. It is a static number. But I can think of
>>>>>> separate the call count.
>>>>>
>>>>> Yep, separate call count for vPSCI and for SSSC itself would be a good
>>>>> thing.
>>>>
>>>>
>>>> Looking a bit more into it, this will not make a real improvement. This
>>>> will be equally difficult to remember to update the call count.
>>>
>>> Nevertheless, I think that it is right thing to hold call count in the
>>> same file, where calls are implemented. This increases chances that call
>>> count will be held in sync.
>>
>>
>> So you are suggesting to implement a function? If so, that's a no-go from
>> my side.
>
> I'm not insist on function if you can propose alternative.
> But why you are against getter function in the first place?

Because a function returning a const value is pretty dumb.

>
> I wanted to propose another approach: define this call count in
> vpsci.h, but there is no vpsci.h, instead you use psci.h, which is confusing
> in itself.

I thought about vpsci.h, but basically you will have only 2 functions in it and
the number of PSCI calls. That's it.

So it is not going to help to update because the header will unlikely need to
change when adding new PSCI call.

[...]

>>
>> I looked at some implementation of SMCCC and those calls are either not
>> handled or the number are not correct.
>
> I agree that *some* implementations can not conform to SMCCC.But, I thought
> you want Xen to follow standards as close as possible...

It is not about cannot conform but only implements partially SMCCC. I could name
ATF for that (yes).

So it makes me more confident the call count is not something people seem to
care.

Cheers,

-- 
Julien Grall

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