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

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

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@redhat.com>
> ---
>   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?