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Mon, 24 Aug 2026 14:42:30 +0000 (UTC) Received: from redhat.com (headnet05.pony-001.prod.iad2.dc.redhat.com [10.2.32.117]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 73B821955F10; Mon, 24 Aug 2026 14:42:23 +0000 (UTC) Date: Mon, 24 Aug 2026 15:42:20 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Dongli Zhang Cc: qemu-devel@nongnu.org, qemu-s390x@nongnu.org, xen-devel@lists.xenproject.org, dave@treblig.org, mst@redhat.com, imammedo@redhat.com, anisinha@redhat.com, philmd@mailo.com, aurelien@aurel32.net, mjrosato@linux.ibm.com, alifm@linux.ibm.com, farman@linux.ibm.com, richard.henderson@linaro.org, iii@linux.ibm.com, david@kernel.org, pasic@linux.ibm.com, borntraeger@linux.ibm.com, cohuck@redhat.com, alex@shazbot.org, clg@redhat.com, akrowiak@linux.ibm.com, jjherne@linux.ibm.com, sstabellini@kernel.org, anthony@xenproject.org, edgar.iglesias@gmail.com, pbonzini@redhat.com, eblake@redhat.com, armbru@redhat.com, joe.jin@oracle.com Subject: Re: [PATCH 3/8] qdev: Support forced device_del in QMP and HMP Message-ID: References: <20260824011420.752806-1-dongli.zhang@oracle.com> <20260824011420.752806-4-dongli.zhang@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260824011420.752806-4-dongli.zhang@oracle.com> User-Agent: Mutt/2.4.0 (2026-06-19) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Sun, Aug 23, 2026 at 06:13:33PM -0700, Dongli Zhang wrote: > Add an optional force argument to the QMP device_del command and expose it > in HMP as "device_del -f". > > When force is requested, qdev_unplug() bypasses the pending deletion guard > and asks the selected hotplug controller to complete removal through its > force_unplug callback. Controllers that do not implement the callback > reject the operation. > > Forced removal bypasses guest cooperation. This sentence is rather missing the punchline.... Force removal bypasses guest cooperation and may result in guest errors, I/O failures, or guest panics. The guest OS cannot be trusted after force removal until a full power cycle has been performed. I'm rather on the fence as to whether it is a good idea to enable this feature or not. If it is used by a cloud admin without knowledge of the guest owner, its use is liable to lead to hard-to-debug/diagnose problems in the guest OS. If a guest OS is not honouring an unplug request and the host owner needs to force reclaim a resource, power off is always there as the failsafe. > diff --git a/qapi/qdev.json b/qapi/qdev.json > index 974cf9c583..cb5b5ad1db 100644 > --- a/qapi/qdev.json > +++ b/qapi/qdev.json > @@ -90,6 +90,11 @@ > # > # @id: the device's ID or QOM path > # > +# @force: if true, remove the device without waiting for guest > +# cooperation. The guest may still be using the device. This can > +# cause guest-visible errors, I/O failures, or guest crashes. I'd want to be warning in a stronger way. This is a dangerous operation that can cause guest-visible errors, I/O failures, or guest crashes. The guest OS state should not be trusted after a forced device removal, until a full power cycle has been performed. > +# (since 11.2) > +# > # Errors: > # - If @id is not a valid device, DeviceNotFound > # > @@ -101,7 +106,9 @@ > # will automatically complete removal for all devices. If a > # guest-side error in the hot removal process is detected, the > # device will not be removed and a `DEVICE_UNPLUG_GUEST_ERROR` > -# event is sent. Some errors cannot be detected. > +# event is sent. Some errors cannot be detected. If @force is > +# true, guest cooperation is bypassed, but backend cleanup is still > +# performed through the device's normal unrealize path. > # > # Since: 0.14 > # > @@ -117,7 +124,7 @@ > # "arguments": { "id": "/machine/peripheral-anon/device[0]" } } > # <- { "return": {} } > ## > -{ 'command': 'device_del', 'data': {'id': 'str'} } > +{ 'command': 'device_del', 'data': {'id': 'str', '*force': 'bool'} } > > ## > # @DEVICE_DELETED: > diff --git a/system/qdev-monitor.c b/system/qdev-monitor.c > index fa3cae246b..ca10a25c46 100644 > --- a/system/qdev-monitor.c > +++ b/system/qdev-monitor.c > @@ -956,11 +956,13 @@ void qdev_unplug(DeviceState *dev, bool force, Error **errp) > error_propagate(errp, local_err); > } With regards, Daniel -- |: https://berrange.com ~~ https://hachyderm.io/@berrange :| |: https://libvirt.org ~~ https://entangle-photo.org :| |: https://pixelfed.art/berrange ~~ https://fstop138.berrange.com :|