Re: [PATCH v4] hw/rtc/mc146818rtc: Make this rtc device target independent

[Thomas Huth <thuth@redhat.com>]

On 02/01/2023 17.47, Bernhard Beschow wrote:
> 
> 
> Am 2. Januar 2023 16:09:08 UTC schrieb Thomas Huth <thuth@redhat.com>:
>> On 02/01/2023 14.36, Thomas Huth wrote:
>>> On 31/12/2022 00.45, Bernhard Beschow wrote:
>>>>
>>>> Am 29. Dezember 2022 10:58:48 UTC schrieb Thomas Huth <thuth@redhat.com>:
>> [...]
>>>>> static uint32_t rtc_periodic_clock_ticks(RTCState *s)
>>>>> {
>>>>> @@ -922,14 +911,15 @@ static void rtc_realizefn(DeviceState *dev, Error **errp)
>>>>>       rtc_set_date_from_host(isadev);
>>>>>
>>>>>       switch (s->lost_tick_policy) {
>>>>> -#ifdef TARGET_I386
>>>>> -    case LOST_TICK_POLICY_SLEW:
>>>>> -        s->coalesced_timer =
>>>>> -            timer_new_ns(rtc_clock, rtc_coalesced_timer, s);
>>>>> -        break;
>>>>> -#endif
>>>>>       case LOST_TICK_POLICY_DISCARD:
>>>>>           break;
>>>>> +    case LOST_TICK_POLICY_SLEW:
>>>>> +        /* Slew tick policy is only available on x86 */
>>>>> +        if (arch_type == QEMU_ARCH_I386) {
>>>>
>>>> This reflects the intention much better than before, which is nice.
>>>>
>>>> How does `arch_type` play together with qemu-system-all? IIUC it should be possible to load all arch backends simultaneously while `arch_type` is an external symbol defined by each arch backend differently. So this seems to conflict.
>>>
>>> I assume that there still will be a main arch_type for the current selected machine? ... not sure how this will exactly work, though ...
>>>
>>>> Can we just add a property such as "slew-tick-policy-available" instead? It should default to false and all x86 machines would need to opt in explicitly.
>>>
>>> Sounds like a good idea, it's certainly better than checking arch_type here ... I'll give it a try, thanks!
>>
>> I've now had a look at this, and it's also getting ugly: Since the property has to be set before realize() is done, the setting of the property has to be added to the mc146818_rtc_init() function. Thus this function would need a new parameter - and it then needs to be changed all over the place, i.e. also for all the non-x86 machines, defeating the idea of a default value...
>>
>> Maybe it makes more sense to check for a TYPE_X86_MACHINE machine type instead?
> 
> Maybe you could base your patch on https://lists.gnu.org/archive/html/qemu-devel/2022-12/msg03795.html ?

That would help, indeed. ... OK, then let's postpone my clean-up until your 
series has landed.

  Thomas