Re: [virtio-dev] [PATCH] content: document console vq detach buffer

[Stefan Hajnoczi <stefanha@redhat.com>]

On Tue, Aug 13, 2019 at 06:21:33PM +0530, Pankaj Gupta wrote:
> This patch documents console special case where vq buffers
> are deleted at port hotunplug time. This behavior is different in
> other devices where vq buffers are deleted at device unplug time.
> 
> Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
> ---
>  content.tex | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/content.tex b/content.tex
> index ee0d7c9..33e8ccc 100644
> --- a/content.tex
> +++ b/content.tex
> @@ -497,6 +497,8 @@ \section{Device Cleanup}\label{sec:General Initialization And Device Operation /
>  of a live virtqueue.
>  
>  Thus a driver MUST ensure a virtqueue isn't live (by device reset) before removing exposed buffers.
> +Console has a special property that when port is detached virtqueue is considered stopped, device
> +must not use any buffers, and it is legal to take buffers out of the device.

The word "detach" is not defined or used in the spec, so it's unclear
what this is supposed to mean.  Is this related to a control message
(VIRTIO_CONSOLE_PORT_OPEN)?

How about:

  The device MUST NOT use buffers after it has sent
  VIRTIO_CONSOLE_PORT_OPEN with value=0 for a port.

I'm not sure what you mean by "take buffers out of the device"?  I guess
you mean the driver can modify the vring because the device isn't
looking.

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