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Tsirkin" , Paolo Bonzini , Eric Blake , qemu-devel@nongnu.org Subject: Re: [PATCH] mc146818rtc: add a way to generate RTC interrupts via QMP In-Reply-To: <20240425133745.464091-1-d-tatianin@yandex-team.ru> (Daniil Tatianin's message of "Thu, 25 Apr 2024 16:37:45 +0300") References: <20240425133745.464091-1-d-tatianin@yandex-team.ru> Date: Fri, 26 Apr 2024 10:39:14 +0200 Message-ID: <87v844y0ul.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.6 Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.669, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Daniil Tatianin 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 > --- > 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? > +# > +# 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? > ## > # @SevState: > #