Re: [PATCH 4/4] virtio-scsi: don't touch scsi devices that are not yet realized

[Paolo Bonzini]

On 16/04/20 22:36, Maxim Levitsky wrote:
> Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1812399
> 
> Suggested-by: Paolo Bonzini <address@hidden>
> Signed-off-by: Maxim Levitsky <address@hidden>
> ---
>  hw/scsi/virtio-scsi.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
> index b0f4a35f81..e360b4e03e 100644
> --- a/hw/scsi/virtio-scsi.c
> +++ b/hw/scsi/virtio-scsi.c
> @@ -35,13 +35,29 @@ static inline int virtio_scsi_get_lun(uint8_t *lun)
>  
>  static inline SCSIDevice *virtio_scsi_device_find(VirtIOSCSI *s, uint8_t 
> *lun)
>  {
> +    SCSIDevice *device = NULL;
> +
>      if (lun[0] != 1) {
>          return NULL;
>      }
>      if (lun[2] != 0 && !(lun[2] >= 0x40 && lun[2] < 0x80)) {
>          return NULL;
>      }
> -    return scsi_device_find(&s->bus, 0, lun[1], virtio_scsi_get_lun(lun));
> +
> +    device = scsi_device_find(&s->bus, 0, lun[1], virtio_scsi_get_lun(lun));
> +
> +    /* This function might run on the IO thread and we might race against
> +     * main thread hot-plugging the device.
> +     *
> +     * We assume that as soon as .realized is set to true we can let
> +     * the user access the device.
> +     */

Likewise this needs to be load-acquire.

Paolo

> +    if (!device || !atomic_read(&device->qdev.realized)) {
> +        return NULL;
> +    }
> +
> +    return device;
>  }
>  
>  void virtio_scsi_init_req(VirtIOSCSI *s, VirtQueue *vq, VirtIOSCSIReq *req)
>