Acked-by: Raphael Norwitz <[email protected]> On Wed, Aug 13, 2025 at 1:01 PM Vladimir Sementsov-Ogievskiy <[email protected]> wrote: > > This field is mostly unused and sometimes confusing (we even have > a TODO-like comment to drop it). Let's finally do. > > The field is used to held VHOST_USER_F_PROTOCOL_FEATURES for vhost-user > and/or VHOST_NET_F_VIRTIO_NET_HDR for vhost-net (which may be > vhoust-user-net). But we can simply recalculte these two flags inplace > from hdev->features, and from net-client for > VHOST_NET_F_VIRTIO_NET_HDR. > > Signed-off-by: Vladimir Sementsov-Ogievskiy <[email protected]> > --- > hw/block/vhost-user-blk.c | 1 - > hw/net/vhost_net.c | 16 ++++++++-------- > hw/scsi/vhost-scsi.c | 1 - > hw/scsi/vhost-user-scsi.c | 1 - > hw/virtio/vdpa-dev.c | 1 - > hw/virtio/vhost-user.c | 19 +++++++++---------- > hw/virtio/virtio-hmp-cmds.c | 2 -- > hw/virtio/virtio-qmp.c | 2 -- > include/hw/virtio/vhost.h | 7 ------- > qapi/virtio.json | 3 --- > 10 files changed, 17 insertions(+), 36 deletions(-) > > diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c > index c0cc5f6942..de7a810c93 100644 > --- a/hw/block/vhost-user-blk.c > +++ b/hw/block/vhost-user-blk.c > @@ -348,7 +348,6 @@ static int vhost_user_blk_connect(DeviceState *dev, Error > **errp) > s->dev.nvqs = s->num_queues; > s->dev.vqs = s->vhost_vqs; > s->dev.vq_index = 0; > - s->dev.backend_features = 0; > > vhost_dev_set_config_notifier(&s->dev, &blk_ops); > > diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c > index 540492b37d..fcee279f0b 100644 > --- a/hw/net/vhost_net.c > +++ b/hw/net/vhost_net.c > @@ -53,7 +53,10 @@ int vhost_net_set_config(struct vhost_net *net, const > uint8_t *data, > > void vhost_net_ack_features(struct vhost_net *net, uint64_t features) > { > - net->dev.acked_features = net->dev.backend_features; > + net->dev.acked_features = > + (qemu_has_vnet_hdr(net->nc) ? 0 : (1ULL << > VHOST_NET_F_VIRTIO_NET_HDR)) > + | (net->dev.features & (1ULL << VHOST_USER_F_PROTOCOL_FEATURES)); > + > vhost_ack_features(&net->dev, net->feature_bits, features); > } > > @@ -256,12 +259,9 @@ struct vhost_net *vhost_net_init(VhostNetOptions > *options) > if (r < 0) { > goto fail; > } > - net->dev.backend_features = qemu_has_vnet_hdr(options->net_backend) > - ? 0 : (1ULL << VHOST_NET_F_VIRTIO_NET_HDR); > net->backend = r; > net->dev.protocol_features = 0; > } else { > - net->dev.backend_features = 0; > net->dev.protocol_features = 0; > net->backend = -1; > > @@ -281,10 +281,10 @@ struct vhost_net *vhost_net_init(VhostNetOptions > *options) > sizeof(struct virtio_net_hdr_mrg_rxbuf))) { > net->dev.features &= ~(1ULL << VIRTIO_NET_F_MRG_RXBUF); > } > - if (~net->dev.features & net->dev.backend_features) { > - fprintf(stderr, "vhost lacks feature mask 0x%" PRIx64 > - " for backend\n", > - (uint64_t)(~net->dev.features & > net->dev.backend_features)); > + if (!qemu_has_vnet_hdr(options->net_backend) && > + (~net->dev.features & (1ULL << VHOST_NET_F_VIRTIO_NET_HDR))) { > + fprintf(stderr, "vhost lacks feature mask 0x%llx for backend\n", > + ~net->dev.features & (1ULL << > VHOST_NET_F_VIRTIO_NET_HDR)); > goto fail; > } > } > diff --git a/hw/scsi/vhost-scsi.c b/hw/scsi/vhost-scsi.c > index cdf405b0f8..d694a25fe2 100644 > --- a/hw/scsi/vhost-scsi.c > +++ b/hw/scsi/vhost-scsi.c > @@ -276,7 +276,6 @@ static void vhost_scsi_realize(DeviceState *dev, Error > **errp) > vqs = g_new0(struct vhost_virtqueue, vsc->dev.nvqs); > vsc->dev.vqs = vqs; > vsc->dev.vq_index = 0; > - vsc->dev.backend_features = 0; > > ret = vhost_dev_init(&vsc->dev, (void *)(uintptr_t)vhostfd, > VHOST_BACKEND_TYPE_KERNEL, 0, errp); > diff --git a/hw/scsi/vhost-user-scsi.c b/hw/scsi/vhost-user-scsi.c > index 25f2d894e7..0c80a271d8 100644 > --- a/hw/scsi/vhost-user-scsi.c > +++ b/hw/scsi/vhost-user-scsi.c > @@ -159,7 +159,6 @@ static int vhost_user_scsi_connect(DeviceState *dev, > Error **errp) > vsc->dev.nvqs = VIRTIO_SCSI_VQ_NUM_FIXED + vs->conf.num_queues; > vsc->dev.vqs = s->vhost_vqs; > vsc->dev.vq_index = 0; > - vsc->dev.backend_features = 0; > > ret = vhost_dev_init(&vsc->dev, &s->vhost_user, VHOST_BACKEND_TYPE_USER, > 0, > errp); > diff --git a/hw/virtio/vdpa-dev.c b/hw/virtio/vdpa-dev.c > index d1da40afc8..3c0eed3e8e 100644 > --- a/hw/virtio/vdpa-dev.c > +++ b/hw/virtio/vdpa-dev.c > @@ -104,7 +104,6 @@ static void vhost_vdpa_device_realize(DeviceState *dev, > Error **errp) > v->dev.vqs = vqs; > v->dev.vq_index = 0; > v->dev.vq_index_end = v->dev.nvqs; > - v->dev.backend_features = 0; > v->started = false; > > ret = vhost_vdpa_get_iova_range(v->vhostfd, &iova_range); > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c > index 1b2879a90c..cf6f53801d 100644 > --- a/hw/virtio/vhost-user.c > +++ b/hw/virtio/vhost-user.c > @@ -1232,7 +1232,7 @@ static int vhost_user_set_vring_base(struct vhost_dev > *dev, > > static bool vhost_user_set_vring_enable_supported(struct vhost_dev *dev) > { > - return virtio_has_feature(dev->backend_features, > + return virtio_has_feature(dev->features, > VHOST_USER_F_PROTOCOL_FEATURES); > } > > @@ -1449,14 +1449,15 @@ static int vhost_user_set_features(struct vhost_dev > *dev, > int ret; > > /* > - * We need to include any extra backend only feature bits that > - * might be needed by our device. Currently this includes the > - * VHOST_USER_F_PROTOCOL_FEATURES bit for enabling protocol > - * features. > + * Don't lose VHOST_USER_F_PROTOCOL_FEATURES, which is vhost-user > + * specific. > */ > - ret = vhost_user_set_u64(dev, VHOST_USER_SET_FEATURES, > - features | dev->backend_features, > - log_enabled); > + if (virtio_has_feature(dev->features, VHOST_USER_F_PROTOCOL_FEATURES)) { > + features |= 1ULL << VHOST_USER_F_PROTOCOL_FEATURES; > + } > + > + ret = vhost_user_set_u64(dev, VHOST_USER_SET_FEATURES, features, > + log_enabled); > > if (virtio_has_feature(dev->protocol_features, > VHOST_USER_PROTOCOL_F_STATUS)) { > @@ -2187,8 +2188,6 @@ static int vhost_user_backend_init(struct vhost_dev > *dev, void *opaque, > (dev->config_ops && dev->config_ops->vhost_dev_config_notifier); > uint64_t protocol_features; > > - dev->backend_features |= 1ULL << VHOST_USER_F_PROTOCOL_FEATURES; > - > err = vhost_user_get_u64(dev, VHOST_USER_GET_PROTOCOL_FEATURES, > &protocol_features); > if (err < 0) { > diff --git a/hw/virtio/virtio-hmp-cmds.c b/hw/virtio/virtio-hmp-cmds.c > index 7d8677bcf0..024904915d 100644 > --- a/hw/virtio/virtio-hmp-cmds.c > +++ b/hw/virtio/virtio-hmp-cmds.c > @@ -175,8 +175,6 @@ void hmp_virtio_status(Monitor *mon, const QDict *qdict) > hmp_virtio_dump_features(mon, s->vhost_dev->features); > monitor_printf(mon, " Acked features:\n"); > hmp_virtio_dump_features(mon, s->vhost_dev->acked_features); > - monitor_printf(mon, " Backend features:\n"); > - hmp_virtio_dump_features(mon, s->vhost_dev->backend_features); > monitor_printf(mon, " Protocol features:\n"); > hmp_virtio_dump_protocols(mon, s->vhost_dev->protocol_features); > } > diff --git a/hw/virtio/virtio-qmp.c b/hw/virtio/virtio-qmp.c > index 3b6377cf0d..e514a4797e 100644 > --- a/hw/virtio/virtio-qmp.c > +++ b/hw/virtio/virtio-qmp.c > @@ -788,8 +788,6 @@ VirtioStatus *qmp_x_query_virtio_status(const char *path, > Error **errp) > qmp_decode_features(vdev->device_id, hdev->features); > status->vhost_dev->acked_features = > qmp_decode_features(vdev->device_id, hdev->acked_features); > - status->vhost_dev->backend_features = > - qmp_decode_features(vdev->device_id, hdev->backend_features); > status->vhost_dev->protocol_features = > qmp_decode_protocols(hdev->protocol_features); > status->vhost_dev->max_queues = hdev->max_queues; > diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h > index 66be6afc88..9f9dd2d46d 100644 > --- a/include/hw/virtio/vhost.h > +++ b/include/hw/virtio/vhost.h > @@ -100,16 +100,9 @@ struct vhost_dev { > * > * @features: available features provided by the backend > * @acked_features: final negotiated features with front-end driver > - * > - * @backend_features: this is used in a couple of places to either > - * store VHOST_USER_F_PROTOCOL_FEATURES to apply to > - * VHOST_USER_SET_FEATURES or VHOST_NET_F_VIRTIO_NET_HDR. Its > - * future use should be discouraged and the variable retired as > - * its easy to confuse with the VirtIO backend_features. > */ > uint64_t features; > uint64_t acked_features; > - uint64_t backend_features; > > /** > * @protocol_features: is the vhost-user only feature set by > diff --git a/qapi/virtio.json b/qapi/virtio.json > index 9d652fe4a8..0aae77340d 100644 > --- a/qapi/virtio.json > +++ b/qapi/virtio.json > @@ -85,8 +85,6 @@ > # > # @acked-features: vhost_dev acked_features > # > -# @backend-features: vhost_dev backend_features > -# > # @protocol-features: vhost_dev protocol_features > # > # @max-queues: vhost_dev max_queues > @@ -106,7 +104,6 @@ > 'vq-index': 'int', > 'features': 'VirtioDeviceFeatures', > 'acked-features': 'VirtioDeviceFeatures', > - 'backend-features': 'VirtioDeviceFeatures', > 'protocol-features': 'VhostDeviceProtocols', > 'max-queues': 'uint64', > 'backend-cap': 'uint64', > -- > 2.48.1 > >
