I have just found this email... sorry for the delay. On 10/01/20 07:10, Yang Zhong wrote: >> No. If virtio-blk works, the bug is in vhost-user-blk; if virtio-blk needs >> no check in cpu count, vhost-user-blk also doesn't. >> >> You need to check first if the bug is in QEMU or the vhost-user-blk server. > > (1). Seabios issue > In init_virtio_blk() function, which set VIRTIO_CONFIG_S_DRIVER_OK > status to qemu vhost-user-blk device. > > // the related code > ...... > status |= VIRTIO_CONFIG_S_DRIVER_OK; > vp_set_status(&vdrive->vp, status); > ...... > > I think there is no need for seabios to set VIRTIO_CONFIG_S_DRIVER_OK > status to qemu vhost-user-blk device.
It does so because it cannot know how it will be used. It could be used by the guest boot loader to load a kernel, for example. SeaBIOS sets DRIVER_OK because it has loaded a driver for the disk; that's exactly what DRIVER_OK signals. > In fact, this time vhost_user_blk_start almost do nothing because > the real guest virtio-blk driver still not started yet. This time, > there is only one vq can be used(this vq should be inited in seabios). > > When the guest virtio-blk driver really start and complet the > probe(), the guest virtio-blk driver will set > VIRTIO_CONFIG_S_DRIVER_OK to vhost-user-blk device again. This > time, this driver will allocate RIGHT queue num according to > MIN(vcpu, num_vqs). Doesn't it first reset the status to 0? > (2). DPDK issue > DPDK does not know the real queue number used by guest virtio-blk > driver and it only know the queue number from vhost-user-blk > commond line. Once the guest virtio-blk driver change the queue > number according to MIN(vcpu, num_vqs), DPDK still use previous > queue number and it think virtio is never ready by > virtio_is_ready() function. What is virtio_is_ready()? The virtio device should not wait for all the queues to be set. A device is ready when it sets DRIVER_OK, and that's it. > or DPDK can get the real queue number by checking if the vring.desc > is NON-NULL. Note that there is no requirement that the driver initializes a consecutive number of virtqueues. It is acceptable for it to initialize virtqueues 0, 1 and 57. It seems like the bug is in DPDK, possibly more than one... Paolo > By the way, vhost SCSI device has the same issue with > vhost-user-blk device. > > Yang > >> Paolo >
