From: Daniil Tatianin <d-tatianin@yandex-team.ru>
To: Markus Armbruster <armbru@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Eric Blake <eblake@redhat.com>,
qemu-devel@nongnu.org
Subject: Re: [PATCH] mc146818rtc: add a way to generate RTC interrupts via QMP
Date: Fri, 26 Apr 2024 12:28:46 +0300 [thread overview]
Message-ID: <12428416-e2d6-435e-87fd-9c278b025898@yandex-team.ru> (raw)
In-Reply-To: <87v844y0ul.fsf@pond.sub.org>
On 4/26/24 11:39 AM, Markus Armbruster wrote:
> 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.
>>
>> Signed-off-by: Daniil Tatianin <d-tatianin@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.
>> ##
>> # @SevState:
>> #
next prev parent reply other threads:[~2024-04-26 9:29 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-25 13:37 [PATCH] mc146818rtc: add a way to generate RTC interrupts via QMP Daniil Tatianin
2024-04-26 8:39 ` Markus Armbruster
2024-04-26 9:28 ` Daniil Tatianin [this message]
2024-04-26 9:47 ` Markus Armbruster
2024-04-26 9:48 ` Philippe Mathieu-Daudé
2024-04-29 9:43 ` Philippe Mathieu-Daudé
2024-04-29 11:32 ` Markus Armbruster
2024-04-29 13:39 ` Philippe Mathieu-Daudé
2024-04-29 14:02 ` Markus Armbruster
2024-05-02 7:30 ` Daniil Tatianin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=12428416-e2d6-435e-87fd-9c278b025898@yandex-team.ru \
--to=d-tatianin@yandex-team.ru \
--cc=armbru@redhat.com \
--cc=eblake@redhat.com \
--cc=mst@redhat.com \
--cc=pbonzini@redhat.com \
--cc=qemu-devel@nongnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.