Commit 1a8c091c authored by Stefan Hajnoczi's avatar Stefan Hajnoczi Committed by Kevin Wolf
Browse files

virtio-scsi: restart DMA after iothread 



When the 'cont' command resumes guest execution the vm change state
handlers are invoked.  Unfortunately there is no explicit ordering
between classic qemu_add_vm_change_state_handler() callbacks.  When two
layers of code both use vm change state handlers, we don't control which
handler runs first.

virtio-scsi with iothreads hits a deadlock when a failed SCSI command is
restarted and completes before the iothread is re-initialized.

This patch uses the new qdev_add_vm_change_state_handler() API to
guarantee that virtio-scsi's virtio change state handler executes before
the SCSI bus children.  This way DMA is restarted after the iothread has
re-initialized.

Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent e965ffa7

hw/scsi/scsi-bus.c

+2 −2
Original line number Diff line number Diff line
@@ -207,8 +207,8 @@ static void scsi_qdev_realize(DeviceState *qdev, Error **errp) 
        error_propagate(errp, local_err);

        return;

    }

    dev->vmsentry = qemu_add_vm_change_state_handler(scsi_dma_restart_cb,

                                                     dev);

    dev->vmsentry = qdev_add_vm_change_state_handler(DEVICE(dev),

            scsi_dma_restart_cb, dev);

}



static void scsi_qdev_unrealize(DeviceState *qdev, Error **errp)

hw/virtio/virtio.c

+2 −2
Original line number Diff line number Diff line
@@ -2362,8 +2362,8 @@ void virtio_init(VirtIODevice *vdev, const char *name, 
    } else {

        vdev->config = NULL;

    }

    vdev->vmstate = qemu_add_vm_change_state_handler(virtio_vmstate_change,

                                                     vdev);

    vdev->vmstate = qdev_add_vm_change_state_handler(DEVICE(vdev),

            virtio_vmstate_change, vdev);

    vdev->device_endian = virtio_default_endian();

    vdev->use_guest_notifier_mask = true;

}