Re: [Qemu-devel] [PATCH 15/17] virtio-serial: Apps should consume all data that guest sends out / Fix virtio api abuse

[Gerd Hoffmann <kraxel@redhat.com>]

>   /* Callback function that's called when the guest sends us data */
> -static size_t flush_buf(VirtIOSerialPort *port, const uint8_t *buf, size_t len)
> +static void flush_buf(VirtIOSerialPort *port, const uint8_t *buf, size_t len)
>   {
>       VirtConsole *vcon = DO_UPCAST(VirtConsole, port, port);
> -    ssize_t ret;
>
> -    ret = qemu_chr_write(vcon->chr, buf, len);
> -
> -    return ret<  0 ? 0 : ret;
> +    qemu_chr_write(vcon->chr, buf, len);
>   }

Ok, so we loose data in case qemu_chr_write wasn't able to write out all 
data?  Nice opportunity to show flow control in action here ;)

On failed+partial writes just put the remaining data into a buffer and 
throttle the port until all buffered data has been successfully written 
to the chardev.

Incremental patch is fine to avoid the chicken-egg issue (throttling is 
added by patch #17).

cheers,
   Gerd