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

[Maxim Levitsky]

On Mon, 2020-05-04 at 13:24 +0200, Paolo Bonzini wrote:
> 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.

Done.

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