On 10/26/2023 4:11 PM, Steve Sistare wrote: > mlx5_vdpa does not preserve userland's view of vring base for the control > queue in the following sequence: > > ioctl VHOST_SET_VRING_BASE > ioctl VHOST_VDPA_SET_STATUS VIRTIO_CONFIG_S_DRIVER_OK > mlx5_vdpa_set_status() > setup_cvq_vring() > vringh_init_iotlb() > vringh_init_kern() > vrh->last_avail_idx = 0; > ioctl VHOST_GET_VRING_BASE > > To fix, restore the value of cvq->vring.last_avail_idx after calling > vringh_init_iotlb. > > Signed-off-by: Steve Sistare <steven.sistare@xxxxxxxxxx> This is a resend, I forgot to cc myself the first time. I don't know if we expect vring_base to be preserved after reset, because the uapi comments say nothing about it. mlx5 *does* preserve base across reset for the the data vq's, but perhaps that is an accident of the implementation. I posted this patch to perhaps avoid future problems. The bug(?) bit me while developing with an older version of qemu, and I can work around it in qemu code. Further, the latest version of qemu always enables svq for the cvq and is not affected by this behavior AFAICT. - Steve _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
