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Tsirkin" , Stefano Garzarella , Cornelia Huck , Luigi Rizzo , Giuseppe Lettieri , Vincenzo Maffione , Eric Blake , Markus Armbruster Subject: [PATCH RFC v3 09/13] vhost-backend: implement extended features support Date: Fri, 18 Jul 2025 10:52:35 +0200 Message-ID: In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.133.124; envelope-from=pabeni@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_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1752828885689116600 Content-Type: text/plain; charset="utf-8" Leverage the kernel extended features manipulation ioctls(), if available, and fallback to old ops otherwise. Error out when setting extended features but kernel support is not available. Note that extended support for get/set backend features is not needed, as the only feature that can be changed belongs to the 64 bit range. Signed-off-by: Paolo Abeni --- v1 -> v2: - synced with kernel ioctl changes --- hw/virtio/vhost-backend.c | 62 ++++++++++++++++++++++++++++++++------- 1 file changed, 51 insertions(+), 11 deletions(-) diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c index 833804dd40..6fde994403 100644 --- a/hw/virtio/vhost-backend.c +++ b/hw/virtio/vhost-backend.c @@ -20,6 +20,11 @@ #include #include =20 +struct vhost_features { + uint64_t count; + uint64_t features[VIRTIO_FEATURES_DWORDS]; +}; + static int vhost_kernel_call(struct vhost_dev *dev, unsigned long int requ= est, void *arg) { @@ -182,12 +187,6 @@ static int vhost_kernel_get_vring_worker(struct vhost_= dev *dev, return vhost_kernel_call(dev, VHOST_GET_VRING_WORKER, worker); } =20 -static int vhost_kernel_set_features(struct vhost_dev *dev, - uint64_t features) -{ - return vhost_kernel_call(dev, VHOST_SET_FEATURES, &features); -} - static int vhost_kernel_set_backend_cap(struct vhost_dev *dev) { uint64_t features; @@ -210,10 +209,51 @@ static int vhost_kernel_set_backend_cap(struct vhost_= dev *dev) return 0; } =20 -static int vhost_kernel_get_features(struct vhost_dev *dev, - uint64_t *features) +static int vhost_kernel_set_features(struct vhost_dev *dev, + const uint64_t *features) { - return vhost_kernel_call(dev, VHOST_GET_FEATURES, features); + struct vhost_features farray; + bool extended_in_use; + int r; + + farray.count =3D VIRTIO_FEATURES_DWORDS; + virtio_features_copy(farray.features, features); + extended_in_use =3D virtio_features_use_extended(farray.features); + + /* + * Can't check for ENOTTY: for unknown ioctls the kernel interprets + * the argument as a virtio queue id and most likely errors out valida= ting + * such id, instead of reporting an unknown operation. + */ + r =3D vhost_kernel_call(dev, VHOST_SET_FEATURES_ARRAY, &farray); + if (!r) { + return 0; + } + + if (extended_in_use) { + error_report("Trying to set extended features without kernel suppo= rt"); + return -EINVAL; + } + return vhost_kernel_call(dev, VHOST_SET_FEATURES, &farray.features[0]); +} + +static int vhost_kernel_get_features(struct vhost_dev *dev, uint64_t *feat= ures) +{ + struct vhost_features farray; + int r; + + farray.count =3D VIRTIO_FEATURES_DWORDS; + r =3D vhost_kernel_call(dev, VHOST_GET_FEATURES_ARRAY, &farray); + if (r) { + memset(&farray, 0, sizeof(farray)); + r =3D vhost_kernel_call(dev, VHOST_GET_FEATURES, &farray.features[= 0]); + } + if (r) { + return r; + } + + virtio_features_copy(features, farray.features); + return 0; } =20 static int vhost_kernel_set_owner(struct vhost_dev *dev) @@ -341,8 +381,8 @@ const VhostOps kernel_ops =3D { .vhost_attach_vring_worker =3D vhost_kernel_attach_vring_worker, .vhost_new_worker =3D vhost_kernel_new_worker, .vhost_free_worker =3D vhost_kernel_free_worker, - .vhost_set_features =3D vhost_kernel_set_features, - .vhost_get_features =3D vhost_kernel_get_features, + .vhost_set_features_ex =3D vhost_kernel_set_features, + .vhost_get_features_ex =3D vhost_kernel_get_features, .vhost_set_backend_cap =3D vhost_kernel_set_backend_cap, .vhost_set_owner =3D vhost_kernel_set_owner, .vhost_get_vq_index =3D vhost_kernel_get_vq_index, --=20 2.50.0