linux-kernel - Re: [PATCHv7 4/4] virtio_console: Add support for remoteproc serial

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Date:	Thu, 1 Nov 2012 13:09:51 +0530
From:	Amit Shah <amit.shah@...hat.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	sjur.brandeland@...ricsson.com,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Ohad Ben-Cohen <ohad@...ery.com>, linux-kernel@...r.kernel.org,
	virtualization@...ts.linux-foundation.org, sjurbren@...il.com
Subject: Re: [PATCHv7 4/4] virtio_console: Add support for remoteproc serial

On (Tue) 23 Oct 2012 [12:17:49], Rusty Russell wrote:
> sjur.brandeland@...ricsson.com writes:
> > From: Sjur Brændeland <sjur.brandeland@...ricsson.com>

> > @@ -1415,7 +1524,16 @@ static void remove_port_data(struct port *port)
> >  
> >  	/* Remove buffers we queued up for the Host to send us data in. */
> >  	while ((buf = virtqueue_detach_unused_buf(port->in_vq)))
> > -		free_buf(buf);
> > +		free_buf(buf, true);
> > +
> > +	/*
> > +	 * Remove buffers from out queue for rproc-serial. We cannot afford
> > +	 * to leak any DMA mem, so reclaim this memory even if this might be
> > +	 * racy for the remote processor.
> > +	 */
> > +	if (is_rproc_serial(port->portdev->vdev))
> > +		while ((buf = virtqueue_detach_unused_buf(port->out_vq)))
> > +			free_buf(buf, true);
> >  }
> 
> This seems wrong; either this is needed even if !is_rproc_serial(), or
> it's not necessary as the out_vq is empty.
> 
> Every path I can see has the device reset (in which case the queues
> should not be active), or we got a VIRTIO_CONSOLE_PORT_REMOVE event (in
> which case, the same).
> 
> I think we can have non-blocking writes which could leave buffers in
> out_vq: Amit?

Those get 'reclaimed' just above this hunk:


static void remove_port_data(struct port *port)
{
	struct port_buffer *buf;

	/* Remove unused data this port might have received. */
	discard_port_data(port);

	reclaim_consumed_buffers(port);

	/* Remove buffers we queued up for the Host to send us data in. */
	while ((buf = virtqueue_detach_unused_buf(port->in_vq)))
	      free_buf(buf, true);

  ...




> >  static void __exit fini(void)
> >  {
> > +	reclaim_dma_bufs();
> 
> Hmm, you didn't protect it here anyway...
> 
> Cheers,
> Rusty.

		Amit
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