The QEMU project is currently moving its bug tracking to another system. For this we need to know which bugs are still valid and which could be closed already. Thus we are setting the bug state to "Incomplete" now.
If the bug has already been fixed in the latest upstream version of QEMU, then please close this ticket as "Fix released". If it is not fixed yet and you think that this bug report here is still valid, then you have two options: 1) If you already have an account on gitlab.com, please open a new ticket for this problem in our new tracker here: https://gitlab.com/qemu-project/qemu/-/issues and then close this ticket here on Launchpad (or let it expire auto- matically after 60 days). Please mention the URL of this bug ticket on Launchpad in the new ticket on GitLab. 2) If you don't have an account on gitlab.com and don't intend to get one, but still would like to keep this ticket opened, then please switch the state back to "New" or "Confirmed" within the next 60 days (other- wise it will get closed as "Expired"). We will then eventually migrate the ticket automatically to the new system (but you won't be the reporter of the bug in the new system and thus you won't get notified on changes anymore). Thank you and sorry for the inconvenience. ** Changed in: qemu Status: New => Incomplete -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1924603 Title: Incorrect feature negotiation for vhost-vdpa netdevice Status in QEMU: Incomplete Bug description: QEMU cmdline: ============= ./x86_64-softmmu/qemu-system-x86_64 -machine accel=kvm -m 2G -hda /gautam/centos75_1.qcow2 -name gautam,process=gautam -enable-kvm -netdev vhost-vdpa,id=mynet0,vhostdev=/dev/vhost-vdpa-0 -device virtio-net-pci,netdev=mynet0,mac=02:AA:BB:DD:00:20,disable-modern=off,page-per-vq=on -cpu host --nographic Host OS: ======== Linux kernel 5.11 running on x86 host Guest OS: ========== CentOS 7.5 Root cause analysis: ===================== For vhost-vdpa netdevice, the feature negotiation results in sending the superset of features received from device in call to get_features vdpa ops callback. During the feature-negotiation phase, the acknowledged feature bits are initialized with backend_features and then checked for supported feature bits in vhost_ack_features(): void vhost_net_ack_features(struct vhost_net *net, uint64_t features) { net->dev.acked_features = net->dev.backend_features; vhost_ack_features(&net->dev, vhost_net_get_feature_bits(net), features); } The vhost_ack_features() function just builds up on the dev.acked_features and never trims it down: void vhost_ack_features(struct vhost_dev *hdev, const int *feature_bits, uint64_t features) { const int *bit = feature_bits; while (*bit != VHOST_INVALID_FEATURE_BIT) { uint64_t bit_mask = (1ULL << *bit); if (features & bit_mask) hdev->acked_features |= bit_mask; bit++; } } Because of this hdev->acked_features is always minimally equal to the value of device features and this is the value that is passed to the device in set_features callback: static int vhost_dev_set_features(struct vhost_dev *dev, bool enable_log) { uint64_t *features = dev->acked_features; ..... r = dev->vhost_ops->*vhost_set_features*(dev, features); } To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1924603/+subscriptions