linux-kernel - Re: [PATCHv5 2/3] virtio_console: Add support for remoteproc serial

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Date:	Thu, 27 Sep 2012 09:22:24 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	sjur.brandeland@...ricsson.com, Amit Shah <amit.shah@...hat.com>
Cc:	linux-kernel@...r.kernel.org,
	virtualization@...ts.linux-foundation.org, sjurbren@...ricsson.com,
	Sjur Brændeland <sjur.brandeland@...ricsson.com>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Ohad Ben-Cohen <ohad@...ery.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCHv5 2/3] virtio_console: Add support for remoteproc serial

sjur.brandeland@...ricsson.com writes:
> From: Sjur Brændeland <sjur.brandeland@...ricsson.com>
>
> Add a simple serial connection driver called
> VIRTIO_ID_RPROC_SERIAL (11) for communicating with a
> remote processor in an asymmetric multi-processing
> configuration.
>
...
>  static struct port_buffer *alloc_buf(struct virtqueue *vq, size_t buf_size,
>  				     int nrbufs)
>  {
>  	struct port_buffer *buf;
>  	size_t alloc_size;
>  
> +	if (is_rproc_serial(vq->vdev) && !irqs_disabled())
> +		reclaim_dma_bufs();

Hmm, you need a gfp_t arg into alloc_buf; your last patch simply changed
them all to GFP_ATOMIC, which makes the console far less memory
friendly.

You check !irqs_disabled() in a couple of places; I think the caller
needs to indicate (possibly by checking for gfp == GFP_KERNEL) whether
it's safe to call reclaim_dma_bufs().

> @@ -838,6 +927,10 @@ static ssize_t port_fops_splice_write(struct pipe_inode_info *pipe,
>  		.u.data = &sgl,
>  	};
>  
> +	/* rproc_serial does not support splice */
> +	if (is_rproc_serial(port->out_vq->vdev))
> +		return -EINVAL;

Why not? ;)

Thanks,
Rusty.
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