Daniil Tatianin <d-tatia...@yandex-team.ru> writes:
> On 4/26/24 11:39 AM, Markus Armbruster wrote:
>
>> Daniil Tatianin <d-tatia...@yandex-team.ru> writes:
>>
>>> This can be used to force-synchronize the time in guest after a long
>>> stop-cont pause, which can be useful for serverless-type workload.
>>>
>>> Signed-off-by: Daniil Tatianin <d-tatia...@yandex-team.ru>
>>> ---
>>> hw/rtc/mc146818rtc.c | 15 +++++++++++++++
>>> include/hw/rtc/mc146818rtc.h | 1 +
>>> qapi/misc-target.json | 16 ++++++++++++++++
>>> 3 files changed, 32 insertions(+)
>>>
>>> diff --git a/hw/rtc/mc146818rtc.c b/hw/rtc/mc146818rtc.c
>>> index f4c1869232..6980a78d5f 100644
>>> --- a/hw/rtc/mc146818rtc.c
>>> +++ b/hw/rtc/mc146818rtc.c
>>> @@ -116,6 +116,21 @@ void qmp_rtc_reset_reinjection(Error **errp)
>>> }
>>> }
>>>
>>> +void qmp_rtc_notify(Error **errp)
>>> +{
>>> + MC146818RtcState *s;
>>> +
>>> + /*
>>> + * See:
>>> + * https://www.kernel.org/doc/Documentation/virtual/kvm/timekeeping.txt
>>> + */
>>> + QLIST_FOREACH(s, &rtc_devices, link) {
>>> + s->cmos_data[RTC_REG_B] |= REG_B_UIE;
>>> + s->cmos_data[RTC_REG_C] |= REG_C_IRQF | REG_C_UF;
>>> + qemu_irq_raise(s->irq);
>>> + }
>>> +}
>>> +
>>
>> Note for later: qmp_rtc_notify() works on all realized mc146818rtc
>> devices. Other kinds of RTC devices are silently ignored. Just like
>> qmp_rtc_reset_reinjection().
>>
>>> static bool rtc_policy_slew_deliver_irq(MC146818RtcState *s)
>>> {
>>> kvm_reset_irq_delivered();
>>> diff --git a/include/hw/rtc/mc146818rtc.h b/include/hw/rtc/mc146818rtc.h
>>> index 97cec0b3e8..5229dffbbd 100644
>>> --- a/include/hw/rtc/mc146818rtc.h
>>> +++ b/include/hw/rtc/mc146818rtc.h
>>> @@ -56,5 +56,6 @@ MC146818RtcState *mc146818_rtc_init(ISABus *bus, int
>>> base_year,
>>> void mc146818rtc_set_cmos_data(MC146818RtcState *s, int addr, int val);
>>> int mc146818rtc_get_cmos_data(MC146818RtcState *s, int addr);
>>> void qmp_rtc_reset_reinjection(Error **errp);
>>> +void qmp_rtc_notify(Error **errp);
>>>
>>> #endif /* HW_RTC_MC146818RTC_H */
>>> diff --git a/qapi/misc-target.json b/qapi/misc-target.json
>>> index 4e0a6492a9..20457b0acc 100644
>>> --- a/qapi/misc-target.json
>>> +++ b/qapi/misc-target.json
>>> @@ -19,6 +19,22 @@
>> ##
>> # @rtc-reset-reinjection:
>> #
>> # This command will reset the RTC interrupt reinjection backlog. Can
>> # be used if another mechanism to synchronize guest time is in effect,
>> # for example QEMU guest agent's guest-set-time command.
>> #
>> # Since: 2.1
>> #
>> # Example:
>> #
>> # -> { "execute": "rtc-reset-reinjection" }
>> # <- { "return": {} }
>> ##
>>> { 'command': 'rtc-reset-reinjection',
>>> 'if': 'TARGET_I386' }
>>>
>>> +##
>>> +# @rtc-notify:
>>> +#
>>> +# Generate an RTC interrupt.
>>
>> Our QMP command to generate NMIs is called inject-nmi. Call this one
>> inject-rtc-irq for consistency? rtc-inject-irq?
>
> This makes sense, I'll rename in the next version. Thanks.
>
>>> +#
>>> +# Since: 9.1
>>> +#
>>> +# Example:
>>> +#
>>> +# -> { "execute": "rtc-notify" }
>>> +# <- { "return": {} }
>>> +#
>>> +##
>>> +{ 'command': 'rtc-notify',
>>> + 'if': 'TARGET_I386' }
>>> +
>>
>> As noted above, both commands silently ignore RTCs other than
>> mc146818rtc.
>>
>> They're only available with TARGET_I386.
>>
>> As long as all machines available with TARGET_I386 can only ever contain
>> mc146818rtc RTCs, ignoring other RTCs is a non-problem in practice.
>>
>> Feels a bit fragile to me. Thoughts?
>
> Feels a bit fragile indeed, but this code has been there since 2.1, and
> I guess no one really found this to be a problem.
Needs a comment at least. I'd put it before the two fragile functions
in mc146818rtc.c.
Even better would be to make the build fail if TARGET_I386 picks up
another RTC, but I don't know how.
>>> ##
>>> # @SevState:
>>> #
