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Mon, 20 Jul 2026 04:23:40 -0700 (PDT) X-Received: by 2002:a05:600c:1d15:b0:494:ca0e:880a with SMTP id 5b1f17b1804b1-4954a3e4855mr156076905e9.12.1784546620420; Mon, 20 Jul 2026 04:23:40 -0700 (PDT) Received: from imammedo ([213.175.37.14]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4955dfa4a97sm101926315e9.4.2026.07.20.04.23.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Jul 2026 04:23:40 -0700 (PDT) Date: Mon, 20 Jul 2026 13:23:37 +0200 From: Igor Mammedov To: "Daniel P. =?UTF-8?B?QmVycmFuZ8Op?=" Cc: Christian Schoenebeck , qemu-devel@nongnu.org, Greg Kurz , Jia Jia Subject: Re: [PATCH 2/3] hw/9pfs/virtio: disable hotpluggable property of virtio-9p device Message-ID: <20260720132337.0110bd9e@imammedo> In-Reply-To: References: <20260713094935.5eda77f9@imammedo> <3767624.R56niFO833@weasel> X-Mailer: Claws Mail 4.4.0 (GTK 3.24.52; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Received-SPF: permerror client-ip=170.10.133.124; envelope-from=imammedo@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=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_PASS=-0.001, T_SPF_PERMERROR=0.01 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: qemu development 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 On Fri, 17 Jul 2026 15:16:14 +0100 Daniel P. Berrang=C3=A9 wrote: > On Fri, Jul 17, 2026 at 04:05:42PM +0200, Christian Schoenebeck wrote: > > On Monday, 13 July 2026 09:49:35 CEST Igor Mammedov wrote: =20 > > > On Fri, 10 Jul 2026 15:40:04 +0100 > > >=20 > > > Daniel P. Berrang=C3=A9 wrote: =20 > > > > On Fri, Jul 10, 2026 at 04:31:51PM +0200, Christian Schoenebeck wro= te: =20 > > > > > On Friday, 10 July 2026 14:51:49 CEST Igor Mammedov wrote: =20 > > > > > > On Fri, 10 Jul 2026 12:49:06 +0200 > > > > > >=20 > > > > > > Christian Schoenebeck wrote: =20 > > > > > > > On Friday, 10 July 2026 12:23:45 CEST Igor Mammedov wrote: =20 > > > > > [...] > > > > > =20 > > > > > > note: I'm looking from pov of hotpluggable PCI device and gener= ic > > > > > > hotplug > > > > > > infra, only. =20 > > > > >=20 > > > > > That's okay, but so far I don't see the relevance for this partic= ular 9p > > > > > device. > > > > > =20 > > > > > > it's not guest users directly, it's how hotplug flow works for = various > > > > > > guest OSes: > > > > > >=20 > > > > > > 1. host plugs device in (-device or device_add) > > > > > > 2. guest OS get's notified one way or another and does what eve= r guest > > > > > > side > > > > > >=20 > > > > > > init needed (incl. mounting share in 9pfs case) =20 > > > > >=20 > > > > > That's not affected by this patch, right? > > > > > =20 > > > > > > opposite flow: > > > > > > 1. host does device_del (basically notify guest to remove devic= e) > > > > > > 2. guest OS frees resources and tells qemu to delete device > > > > > > 3. qemu process remove event (which incl. unrealize as part of > > > > > > destroying > > > > > > device) =20 > > > > >=20 > > > > > And that's not affected by this patch either, right? =20 > > >=20 > > > the patch would break unplug flow by effectively removing 'eject' knob > > > from guest side, which is part of unplug flow. =20 > >=20 > > These are two different things: device_del would not be affected by thi= s.=20 > >=20 > > 1. Ejecting the device from host side e.g. via QMP would still work. > >=20 > > vs. > >=20 > > 2. Ejecting from guest side OTOH would be disabled. > >=20 > > It is also different from regular block devices where you have convenie= nt ways > > to eject a block device on guest OSes. For a virtio-9p device it is not= that > > easy. =20 >=20 > Igor can correct me if I'm wrong, but IIUC there's no distinction > to those 2 scenarios from the guest POV. >=20 > A "device_del" in QMP does not actually delete a device from the > QEMU POV. Rather it triggers an ACPI notification to the geust > OS, that the operator wants to unplug the device. The guest OS > then honours (or not) that by initiating a guest side "eject". > IOW disabling guest initiated eject would break device_del too > AFAIK. That's how it works. Sorry if I wasn't able to convey the message in my previous replies. >=20 > With regards, > Daniel