Re: [PATCH v1] mc146818rtc: add a way to generate RTC interrupts via QMP

[Markus Armbruster]

Daniil Tatianin <d-tatianin@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.
>
> Also add a comment to highlight the fact that this (and one other QMP
> command) only works for the MC146818 RTC controller.
>
> Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru>
> ---
>
> Changes since v0:
> - Rename to rtc-inject-irq to match other similar API
> - Add a comment to highlight that this only works for the I386 RTC
>
> ---
>  hw/rtc/mc146818rtc.c         | 20 ++++++++++++++++++++
>  include/hw/rtc/mc146818rtc.h |  1 +
>  qapi/misc-target.json        | 16 ++++++++++++++++
>  3 files changed, 37 insertions(+)
>
> diff --git a/hw/rtc/mc146818rtc.c b/hw/rtc/mc146818rtc.c
> index f4c1869232..8501b55cbd 100644
> --- a/hw/rtc/mc146818rtc.c
> +++ b/hw/rtc/mc146818rtc.c
> @@ -107,6 +107,11 @@ static void rtc_coalesced_timer_update(MC146818RtcState 
> *s)
>  static QLIST_HEAD(, MC146818RtcState) rtc_devices =
>      QLIST_HEAD_INITIALIZER(rtc_devices);
>  
> +/*
> + * NOTE:
> + * The two QMP functions below are _only_ implemented for the MC146818.
> + * All other RTC devices ignore this.
> + */
>  void qmp_rtc_reset_reinjection(Error **errp)
>  {
>      MC146818RtcState *s;
> @@ -116,6 +121,21 @@ void qmp_rtc_reset_reinjection(Error **errp)
>      }
>  }
>  
> +void qmp_rtc_inject_irq(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);
> +    }
> +}
> +
>  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..6cd9761d80 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_inject_irq(Error **errp);
>  
>  #endif /* HW_RTC_MC146818RTC_H */
> diff --git a/qapi/misc-target.json b/qapi/misc-target.json
> index 4e0a6492a9..d84a5d07a2 100644
> --- a/qapi/misc-target.json
> +++ b/qapi/misc-target.json
> @@ -19,6 +19,22 @@
>  { 'command': 'rtc-reset-reinjection',
>    'if': 'TARGET_I386' }
>  
> +##
> +# @rtc-inject-irq:
> +#
> +# Inject an RTC interrupt.

Your cover letter explains what this could be good for.  Would it make
sense to explain it here, too?

> +#
> +# Since: 9.1
> +#
> +# Example:
> +#
> +#     -> { "execute": "rtc-inject-irq" }
> +#     <- { "return": {} }
> +#
> +##
> +{ 'command': 'rtc-inject-irq',
> +  'if': 'TARGET_I386' }
> +
>  ##
>  # @SevState:
>  #