Re: [Qemu-devel] [PATCH 2/3] virtio: access ISR atomically

[Michael S. Tsirkin]

On Wed, Nov 16, 2016 at 07:05:50PM +0100, Paolo Bonzini wrote:
> @@ -1318,10 +1318,18 @@ void virtio_del_queue(VirtIODevice *vdev, int n)
>      vdev->vq[n].vring.num_default = 0;
>  }
>  
> +static void virtio_set_isr(VirtIODevice *vdev, int value)
> +{
> +    uint8_t old = atomic_read(&vdev->isr);
> +    if ((old & value) != value) {
> +        atomic_or(&vdev->isr, value);
> +    }
> +}
> +

Paolo, can you pls comment on why is it done like this,
as opposed to a single atomic_or?

-- 
MST