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Sat, 24 Apr 2021 07:28:07 +0200 (CEST) From: Markus Armbruster To: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Subject: Re: Resetting non-qdev children in a 3-phase reset device References: <87y2datpyw.fsf@dusky.pond.sub.org> <5570bf5a-3cab-c30c-2c21-0ab02543199e@amsat.org> <2f4155ca-ee84-75f0-8b35-aac6b18ee4f0@amsat.org> <3dcb8efa-8f6b-0f45-a753-cc58d3bf9855@amsat.org> Date: Sat, 24 Apr 2021 07:28:07 +0200 In-Reply-To: <3dcb8efa-8f6b-0f45-a753-cc58d3bf9855@amsat.org> ("Philippe =?utf-8?Q?Mathieu-Daud=C3=A9=22's?= message of "Sat, 24 Apr 2021 01:28:56 +0200") Message-ID: <87im4cb6ag.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=armbru@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=216.205.24.124; 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=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, 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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Damien Hedde , Peter Maydell , Eduardo Habkost , QEMU Developers Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Philippe Mathieu-Daud=C3=A9 writes: > On 4/24/21 1:06 AM, Philippe Mathieu-Daud=C3=A9 wrote: > >> Looking at qemu_register_reset() uses I found this commit: >>=20 >> commit 0c7322cfd3fd382c0096c2a9f00775818a878e13 >> Date: Mon Jun 29 08:21:10 2015 +0200 >>=20 >> watchdog/diag288: correctly register for system reset requests >>=20 >> The diag288 watchdog is no sysbus device, therefore it doesn't get >> triggered on resets automatically using dc->reset. >>=20 >> Let's register the reset handler manually, so we get correctly notified >> again when a system reset was requested. Also reset the watchdog on >> subsystem resets that don't trigger a full system reset. >>=20 >> Why is the reset() handler in DeviceClass and not in SysbusDeviceClass >> if "Only sysbus devices get reset"? ... > > Ah, probably because the problem is generic to all busses (ISA, ...) > and not just sysbus. diag288 is a bus-less device. Propagating reset from the root of the qtree to the leaves won't reach it, because the qtree contains only the devices that plug into a qbus. >>>> Sysbus may habe been a design mistake. It goes back the qdev design >>>> assumption "every device plugs into exactly one bus, every bus is part >>>> of exactly one device, and the main system bus is the root of this >>>> tree". The assumption ceased to hold long ago, but we still have >>>> sysbus.