From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E38C6C4345F for ; Mon, 29 Apr 2024 11:32:54 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1s1PFK-0001jV-Ks; Mon, 29 Apr 2024 07:32:34 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1s1PFI-0001iz-3B for qemu-devel@nongnu.org; Mon, 29 Apr 2024 07:32:32 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1s1PFG-0006JZ-Dk for qemu-devel@nongnu.org; Mon, 29 Apr 2024 07:32:31 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1714390349; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=YBVpLm3jvO/mJQAtmby+Y0r8Hl61Y109EcKFsoMWi9Y=; b=VghfCg2WXZ70U3OSwjyhENqvh7NhC6lV/jorBWpPlSesRmViJz6utoIM0kq7e3Of6J2G4K rFzZKpnwSrVTYL9C9W8Zb1PG6eR3NNOKaDl989B05DkCHkiJx3hmzr5O9CfkJR1twzW5ln p7YXZV0ZgIC9ooIANHHOqZ2wCu8VlZA= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-5-rkiV8AO3NLaQiE0zI7TsoQ-1; Mon, 29 Apr 2024 07:32:28 -0400 X-MC-Unique: rkiV8AO3NLaQiE0zI7TsoQ-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id B95FF38000AC; Mon, 29 Apr 2024 11:32:27 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.247]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 81F1040C5C2; Mon, 29 Apr 2024 11:32:27 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id A17BD21E66E5; Mon, 29 Apr 2024 13:32:26 +0200 (CEST) From: Markus Armbruster To: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Cc: Daniil Tatianin , "Michael S. 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: <11c78645-e87b-4a43-8191-a73540c364a9@linaro.org> ("Philippe =?utf-8?Q?Mathieu-Daud=C3=A9=22's?= message of "Fri, 26 Apr 2024 11:48:12 +0200") References: <20240425133745.464091-1-d-tatianin@yandex-team.ru> <87v844y0ul.fsf@pond.sub.org> <11c78645-e87b-4a43-8191-a73540c364a9@linaro.org> Date: Mon, 29 Apr 2024 13:32:26 +0200 Message-ID: <87plu8ieut.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.10 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: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.987, 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 Philippe Mathieu-Daud=C3=A9 writes: > Hi Daniil, Markus, > > On 26/4/24 10:39, Markus Armbruster wrote: >> Daniil Tatianin writes: >>=20 >>> 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/timekeepin= g.txt >>> + */ >>> + QLIST_FOREACH(s, &rtc_devices, link) { >>> + s->cmos_data[RTC_REG_B] |=3D REG_B_UIE; >>> + s->cmos_data[RTC_REG_C] |=3D 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(). > > IMO to avoid any future ambiguity (in heterogeneous machines), this > command must take a QOM device path (or a list of) and only notify > those. Let's compare: =E2=80=A2 With QOM path: =C2=B7 You need to know the machine's RTC device(s). Unfortunately, this is bothersome, as the QOM path is not stable. For Q35, it's generally "/machine/unattached/device[N]/rtc", but N varies with configuration (TCG N=3D2, KVM N=3D3 for me), and it might vary with machine type version. That's because the machine code creates ICH9-LPC without a proper name. We do that a lot. I hate it. Likewise for i440FX with PIIX3 instead of ICH9-LPC. For isapc, it's /machine/unattached/device[3]. I suspect the 3 isn't reliable there, either. microvm doesn't seem to have an RTC by default. =C2=B7 If the device so named doesn't support IRQ inject, the command should fail. =C2=B7 Could be generalized to non-RTC devices when that's useful. =E2=80=A2 Broadcast: =C2=B7 You don't need to know the machine's RTC device(s). =C2=B7 If there are multiple RTC devices that support IRQ inject, we inje= ct for each of them. There is no way to select specific RTCs. =C2=B7 If there is no RTC device that supports IRQ inject, the command do= es nothing silently. I don't like silent failures. It could be made to fail instead. If it wasn't for the unstable QOM path problem, I'd advise against the broadcast interface. Thoughts?