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Tsirkin" To: Christian Speich Cc: qemu-devel@nongnu.org, Stefano Garzarella , Alex =?iso-8859-1?Q?Benn=E9e?= Subject: Re: [PATCH] virtio: vhost-user-device: Make user creatable again Message-ID: <20250925053005-mutt-send-email-mst@kernel.org> References: <20250919-vhost-user-device-creatable-v1-1-87eefeea7f68@avm.de> <20250919160526-mutt-send-email-mst@kernel.org> <32x5pe3iz6v2vu5imktyxwajk4vdhamhc7yhfmtzuylcvdkunl@wvdfyo23zueh> <20250922065614-mutt-send-email-mst@kernel.org> <4yg4y2miiso6c4c6qtlowji6ak3kid5g66ncen4uljsone67ta@c6s22jbk4ckz> <20250922103658-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Received-SPF: pass client-ip=170.10.133.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.444, 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_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-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 On Thu, Sep 25, 2025 at 09:56:02AM +0200, Christian Speich wrote: > On Mon, Sep 22, 2025 at 10:37:40AM -0400, Michael S. Tsirkin wrote: > > On Mon, Sep 22, 2025 at 01:11:33PM +0200, Christian Speich wrote: > > > On Mon, Sep 22, 2025 at 06:56:31AM -0400, Michael S. Tsirkin wrote: > > > > On Mon, Sep 22, 2025 at 12:40:33PM +0200, Christian Speich wrote: > > > > > On Fri, Sep 19, 2025 at 04:07:19PM -0400, Michael S. Tsirkin wrote: > > > > > > On Fri, Sep 19, 2025 at 04:30:53PM +0200, Christian Speich wrote: > > > > > > > This removes the change introduced in [1] that prevents the use of > > > > > > > vhost-user-device and vhost-user-device-pci on unpatched QEMU builds. > > > > > > > > > > > > > > [1]: 6275989647efb708f126eb4f880e593792301ed4 > > > > > > > > > > > > > > Signed-off-by: Christian Speich > > > > > > > --- > > > > > > > vhost-user-device and vhost-user-device-pci started out as user > > > > > > > creatable devices. This was changed in [1] when the vhost-user-base was > > > > > > > introduced. > > > > > > > > > > > > > > The reason given is to prevent user confusion. Searching qemu-discuss or > > > > > > > google for "vhost-user-device" I've seen no confused users. > > > > > > > > > > > > > > Our use case is to provide wifi emulation using "vhost-user-device-pci", > > > > > > > which currently is working fine with the QEMU 9.0.2 present in Ubuntu > > > > > > > 24.04. With newer QEMU versions we now need to patch, distribute and > > > > > > > maintain our own QEMU packages, which is non-trivial. > > > > > > > > > > > > > > So I want to propose lifting this restriction to make this feature > > > > > > > usable without a custom QEMU. > > > > > > > > > > > > > > [1]: 6275989647efb708f126eb4f880e593792301ed4 > > > > > > > > > > > > The confusion is after someone reuses the ID you are claiming without > > > > > > telling anyone and then linux guests will start binding that driver to > > > > > > your device. > > > > > > > > > > Thanks for clarifciation, In our use-case we use mac80211_hwsim which is > > > > > in linux upstream (with the ID 29). So I think a potential reuse here > > > > > is something that linux upstream already deals with. > > > > > > > > So just allow that one? > > > > > > That would solve our problem. > > > > > > However, I'm finding it somwhat odd to artifically force the user only use > > > QEMU it the "allowed way". I'd much rather see that virtio-user-device is > > > usuable as is (and mac80211_hwsim is not a special case and just works). > > > > > > Regards, > > > Christian > > > > We can combine both. Want to try? > > I'm not sure what both means here? > > Greetings, > Christian Both add a generic device with a declaration that it is unsupported and maybe "x-" name prefix, for developers, and a supported mac80211_hwsim device, for users. > > > > > > > > > > > > > > > > > > > > > > > > > > We want people doing this kind of thing to *at a minimum* > > > > > > go ahead and register a device id with the virtio TC, > > > > > > but really to write and publish a spec. > > > > > > > > > > I understand this desire, I'm not sure how this relates with the ability > > > > > to let a user create a vhost-user-device or not. > > > > > > > > > > Kind Regards, > > > > > Christian > > > > > > > > > > > > > > > > > > > > > > > > --- > > > > > > > docs/system/devices/vhost-user.rst | 10 ---------- > > > > > > > hw/virtio/vhost-user-device-pci.c | 3 --- > > > > > > > hw/virtio/vhost-user-device.c | 3 --- > > > > > > > 3 files changed, 16 deletions(-) > > > > > > > > > > > > > > diff --git a/docs/system/devices/vhost-user.rst b/docs/system/devices/vhost-user.rst > > > > > > > index 35259d8ec7c666aa0c56497b8261f48d77216ad5..2d130f9767dbb1cbb85cef43c63dc9a8d7b30d4a 100644 > > > > > > > --- a/docs/system/devices/vhost-user.rst > > > > > > > +++ b/docs/system/devices/vhost-user.rst > > > > > > > @@ -73,16 +73,6 @@ all the required parameters including: > > > > > > > - The ``num_vqs`` it needs and their ``vq_size`` > > > > > > > - The ``config_size`` if needed > > > > > > > > > > > > > > -.. note:: > > > > > > > - To prevent user confusion you cannot currently instantiate > > > > > > > - vhost-user-device without first patching out:: > > > > > > > - > > > > > > > - /* Reason: stop inexperienced users confusing themselves */ > > > > > > > - dc->user_creatable = false; > > > > > > > - > > > > > > > - in ``vhost-user-device.c`` and ``vhost-user-device-pci.c`` file and > > > > > > > - rebuilding. > > > > > > > - > > > > > > > vhost-user daemon > > > > > > > ================= > > > > > > > > > > > > > > diff --git a/hw/virtio/vhost-user-device-pci.c b/hw/virtio/vhost-user-device-pci.c > > > > > > > index f10bac874e78429c633752a4ce9db28385b3bb07..c76a856c9b9a67d941a93929244216658ff2a156 100644 > > > > > > > --- a/hw/virtio/vhost-user-device-pci.c > > > > > > > +++ b/hw/virtio/vhost-user-device-pci.c > > > > > > > @@ -38,9 +38,6 @@ static void vhost_user_device_pci_class_init(ObjectClass *klass, > > > > > > > VirtioPCIClass *k = VIRTIO_PCI_CLASS(klass); > > > > > > > PCIDeviceClass *pcidev_k = PCI_DEVICE_CLASS(klass); > > > > > > > > > > > > > > - /* Reason: stop users confusing themselves */ > > > > > > > - dc->user_creatable = false; > > > > > > > - > > > > > > > k->realize = vhost_user_device_pci_realize; > > > > > > > set_bit(DEVICE_CATEGORY_INPUT, dc->categories); > > > > > > > pcidev_k->vendor_id = PCI_VENDOR_ID_REDHAT_QUMRANET; > > > > > > > diff --git a/hw/virtio/vhost-user-device.c b/hw/virtio/vhost-user-device.c > > > > > > > index 3939bdf755222a281da8ca22243d7d4f16990a66..1bea496afd0137ba9b42009f6252acf6800528d1 100644 > > > > > > > --- a/hw/virtio/vhost-user-device.c > > > > > > > +++ b/hw/virtio/vhost-user-device.c > > > > > > > @@ -41,9 +41,6 @@ static void vud_class_init(ObjectClass *klass, const void *data) > > > > > > > { > > > > > > > DeviceClass *dc = DEVICE_CLASS(klass); > > > > > > > > > > > > > > - /* Reason: stop inexperienced users confusing themselves */ > > > > > > > - dc->user_creatable = false; > > > > > > > - > > > > > > > device_class_set_props(dc, vud_properties); > > > > > > > dc->vmsd = &vud_vmstate; > > > > > > > set_bit(DEVICE_CATEGORY_INPUT, dc->categories); > > > > > > > > > > > > > > --- > > > > > > > base-commit: e7c1e8043a69c5a8efa39d4f9d111f7c72c076e6 > > > > > > > change-id: 20250919-vhost-user-device-creatable-b7f9b7b5bfb2 > > > > > > > > > > > > > > Best regards, > > > > > > > -- > > > > > > > Christian Speich > > > > > > > > > > > > > > > > > > > > > > > >