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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: <12428416-e2d6-435e-87fd-9c278b025898@yandex-team.ru> (Daniil Tatianin's message of "Fri, 26 Apr 2024 12:28:46 +0300") References: <20240425133745.464091-1-d-tatianin@yandex-team.ru> <87v844y0ul.fsf@pond.sub.org> <12428416-e2d6-435e-87fd-9c278b025898@yandex-team.ru> Date: Fri, 26 Apr 2024 11:47:13 +0200 Message-ID: <87le50wj4u.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 10.11.54.8 Received-SPF: pass client-ip=170.10.129.124; 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: > On 4/26/24 11:39 AM, Markus Armbruster wrote: > >> 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? > > 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: >>> #