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

Hi Rusty,

The free-outside-interrupt issue is usually dealt with by offloading to
a wq, but your variant works (and isn't too ugly).

Ok, thanks.

quoted

+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;

...

Looks like this should be an easy noop even if !is_rproc_serial.

Ok,  I'll drop the superfluous check before calling reclaim_dma_bufs().

quoted

@@ -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?

Hm, the remote device could potentially freeze whenever. So I think we
should handle the situation where buffer are stuck in the out-queue for
the rproc_serial device. But I'll move this piece of code into a new
follow-up patch so we can handle this issue separately.

Thanks,
Sjur