Hi Michael and all, I have started researching a qemu / ovs / dpdk bug:
https://inbox.dpdk.org/dev/322122fb-619d-96f6-5c3e-9eabdbf38...@redhat.com/T/ that seems to be affecting multiple parties in the telco space, and during this process I noticed that qemu/hw/virtio/virtio.c does not do a full virtio reset in virtio_set_status, when receiving a status value of 0. It seems it has always been this way, so I am clearly missing / forgetting something basic, I checked the virtio spec at https://docs.oasis-open.org/ and from: " 4.1.4.3 Common configuration structure layout device_status The driver writes the device status here (see 2.1). Writing 0 into this field resets the device. " and " 2.4.1 Device Requirements: Device Reset A device MUST reinitialize device status to 0 after receiving a reset. " I would conclude that in virtio.c::virtio_set_status we should unconditionally do a full virtio_reset. Instead, we have just the check: if ((vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) != (val & VIRTIO_CONFIG_S_DRIVER_OK)) { virtio_set_started(vdev, val & VIRTIO_CONFIG_S_DRIVER_OK); } which just sets the started field, and then we have the call to the virtio device class set_status (virtio_net...), but the VirtioDevice is not fully reset, as per the virtio_reset() call we are missing: " vdev->start_on_kick = false; vdev->started = false; vdev->broken = false; vdev->guest_features = 0; vdev->queue_sel = 0; vdev->status = 0; vdev->disabled = false; qatomic_set(&vdev->isr, 0); vdev->config_vector = VIRTIO_NO_VECTOR; virtio_notify_vector(vdev, vdev->config_vector); for(i = 0; i < VIRTIO_QUEUE_MAX; i++) { ... initialize vdev->vq[i] ... } " Doing a full reset seems to fix the problem for me, so I can send tentative patches if necessary, but what am I missing here? Thanks, Claudio -- Claudio Fontana Engineering Manager Virtualization, SUSE Labs Core SUSE Software Solutions Italy Srl
