Re: [Qemu-devel] [PATCH v8 7/7] virtio-console: Enable port throttling when chardev is slow to consume data

[Amit Shah]

On (Wed) Dec 01 2010 [11:30:58], Paul Brook wrote:
> >  /* Callback function that's called when the guest sends us data */
> >  static void flush_buf(VirtIOSerialPort *port, const uint8_t *buf, size_t
> > len) {
> >      VirtConsole *vcon = DO_UPCAST(VirtConsole, port, port);
> > +    int ret;
> > 
> > -    qemu_chr_write(vcon->chr, buf, len);
> > +    ret = qemu_chr_write(vcon->chr, buf, len);
> > +    if (ret == -EAGAIN) {
> > +        virtio_serial_throttle_port(port, true);
> > +    }
> >  }
> 
> This looks wrong. It will loose data in the case of a partial write
> (i.e. ret < len)

That doesn't happen currently (qemu_chr_write doesn't return a value > 0
but < len).

I had code in there to handle it, but that would change behaviour for
current users of qemu_chr_write(), which is a risk.

                Amit