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Date: Fri, 8 Dec 2017 11:08:07 +0100
From: Cornelia Huck <cohuck@redhat.com>
Message-ID: <20171208110807.7239fb36.cohuck@redhat.com>
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References: <20171207191726-musend-email-mst@kernel.org>
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Subject: Re: [Qemu-devel] question on virtio ccw
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: qemu-devel@nongnu.org

On Thu, 7 Dec 2017 19:18:44 +0200
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> I see this in ccw in qemu:
> 
>             if (virtio_set_status(vdev, status) == 0) {
>                 if (vdev->status == 0) {
>                     virtio_ccw_reset_virtio(dev, vdev);
>                 }
>                 if (status & VIRTIO_CONFIG_S_DRIVER_OK) {
>                     virtio_ccw_start_ioeventfd(dev);
>                 }
>                 sch->curr_status.scsw.count = ccw.count - sizeof(status);
>                 ret = 0;
>             } else {
>                 /* Trigger a command reject. */
>                 ret = -ENOSYS;
>             }
> 
> virtio_set_status on success sets vdev->status to status.
> Why check vdev->status in one place and status in another?
> 

Probably for symmetry with the check whether to stop ioeventfd right
above. But it does not really matter one way or the other.