sjur.brandel...@stericsson.com writes:
> From: Sjur Brændeland <sjur.brandel...@stericsson.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.
>
> This implementation reuses the existing virtio_console
> implementation, and adds support for DMA allocation
> of data buffers and disables use of tty console and
> the virtio control queue.
>
> Signed-off-by: Sjur Brændeland <sjur.brandel...@stericsson.com>
The free-outside-interrupt issue is usually dealt with by offloading to
a wq, but your variant works (and isn't too ugly).
> + /* dma_free_coherent requires interrupts to be enabled. */
> + if (!can_sleep) {
> + /* queue up dma-buffers to be freed later */
> + spin_lock_irqsave(&dma_bufs_lock, flags);
> + list_add_tail(&buf->list, &pending_free_dma_bufs);
> + spin_unlock_irqrestore(&dma_bufs_lock, flags);
> + return;
> + }
> + dma_free_coherent(buf->dev, buf->size, buf->buf, buf->dma);
> +
> + /* Release device refcnt and allow it to be freed */
> + put_device(buf->dev);
...
> +static void reclaim_dma_bufs(void)
> +{
> + unsigned long flags;
> + struct port_buffer *buf, *tmp;
> + LIST_HEAD(tmp_list);
> +
> + if (list_empty(&pending_free_dma_bufs))
> + return;
> +
> + /* Create a copy of the pending_free_dma_bufs while holding the lock */
> + spin_lock_irqsave(&dma_bufs_lock, flags);
> + list_cut_position(&tmp_list, &pending_free_dma_bufs,
> + pending_free_dma_bufs.prev);
> + spin_unlock_irqrestore(&dma_bufs_lock, flags);
> +
> + /* Release the dma buffers, without irqs enabled */
> + list_for_each_entry_safe(buf, tmp, &tmp_list, list) {
> + list_del(&buf->list);
> + free_buf(buf, true);
> + }
> +}
Looks like this should be an easy noop even if !is_rproc_serial.
> +
> static struct port_buffer *alloc_buf(struct virtqueue *vq, size_t buf_size,
> int pages)
> {
> struct port_buffer *buf;
>
> + if (is_rproc_serial(vq->vdev))
> + reclaim_dma_bufs();
> +
...
> @@ -904,6 +1000,8 @@ static int port_fops_release(struct inode *inode, struct
> file *filp)
> reclaim_consumed_buffers(port);
> spin_unlock_irq(&port->outvq_lock);
>
> + if (is_rproc_serial(port->portdev->vdev))
> + reclaim_dma_bufs();
So these are redundant.
> @@ -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?
> static void __exit fini(void)
> {
> + reclaim_dma_bufs();
Hmm, you didn't protect it here anyway...
Cheers,
Rusty.
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