Re: [PATCH 01/13] virtio-scsi: avoid race between unplug and transport event

[Stefan Hajnoczi <stefanha@xxxxxxxxxx>]

On Mon, Apr 03, 2023 at 10:47:11PM +0200, Philippe Mathieu-Daudé wrote:
> On 3/4/23 20:29, Stefan Hajnoczi wrote:
> > Only report a transport reset event to the guest after the SCSIDevice
> > has been unrealized by qdev_simple_device_unplug_cb().
> > 
> > qdev_simple_device_unplug_cb() sets the SCSIDevice's qdev.realized field
> > to false so that scsi_device_find/get() no longer see it.
> > 
> > scsi_target_emulate_report_luns() also needs to be updated to filter out
> > SCSIDevices that are unrealized.
> > 
> > These changes ensure that the guest driver does not see the SCSIDevice
> > that's being unplugged if it responds very quickly to the transport
> > reset event.
> > 
> > Signed-off-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
> > ---
> >   hw/scsi/scsi-bus.c    |  3 ++-
> >   hw/scsi/virtio-scsi.c | 18 +++++++++---------
> >   2 files changed, 11 insertions(+), 10 deletions(-)
> > 
> > diff --git a/hw/scsi/scsi-bus.c b/hw/scsi/scsi-bus.c
> > index c97176110c..f9bd064833 100644
> > --- a/hw/scsi/scsi-bus.c
> > +++ b/hw/scsi/scsi-bus.c
> > @@ -487,7 +487,8 @@ static bool 
> > scsi_target_emulate_report_luns(SCSITargetReq *r)
> >               DeviceState *qdev = kid->child;
> >               SCSIDevice *dev = SCSI_DEVICE(qdev);
> > -            if (dev->channel == channel && dev->id == id && dev->lun != 0) 
> > {
> > +            if (dev->channel == channel && dev->id == id && dev->lun != 0 
> > &&
> > +                qatomic_load_acquire(&dev->qdev.realized)) {
> 
> Would this be more useful as a qdev_is_realized() helper?

Yes. There are no other users, but I think a helper makes sense.

Stefan

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