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virtio-serial: make flow control explicit in virtio-console

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virtio-console.c used to return a value less than the number of bytes
asked to be written out to a chardev backend in case the backend is not
writable.  virtio-serial-bus.c then implicitly enabled flow control for
that port.

Make this explicit instead.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Message-id: f5ec50b068c25422256e499cf4adc06d353bf394.1362505276.git.amit.shah@redhat.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Amit Shah 2013-03-05 23:21:35 +05:30 committed by Anthony Liguori
parent 7df4d4578f
commit d6258c93a7
2 changed files with 10 additions and 26 deletions
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17
hw/virtio-console.c
View File

@ -47,20 +47,21 @@ static ssize_t flush_buf(VirtIOSerialPort *port, const uint8_t *buf, size_t len)
ret = qemu_chr_fe_write(vcon->chr, buf, len);
trace_virtio_console_flush_buf(port->id, len, ret);
if (ret < 0) {
if (ret <= 0) {
VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);
/*
* Ideally we'd get a better error code than just -1, but
* that's what the chardev interface gives us right now. If
* we had a finer-grained message, like -EPIPE, we could close
* this connection. Absent such error messages, the most we
* can do is to return 0 here.
*
* This will prevent stray -1 values to go to
* virtio-serial-bus.c and cause abort()s in
* do_flush_queued_data().
* this connection.
*/
ret = 0;
qemu_chr_fe_add_watch(vcon->chr, G_IO_OUT, chr_write_unblocked, vcon);
if (!k->is_console) {
virtio_serial_throttle_port(port, true);
qemu_chr_fe_add_watch(vcon->chr, G_IO_OUT, chr_write_unblocked,
vcon);
}
}
return ret;
}

19
hw/virtio-serial-bus.c
View File

@ -172,24 +172,7 @@ static void do_flush_queued_data(VirtIOSerialPort *port, VirtQueue *vq,
port->elem.out_sg[i].iov_base
+ port->iov_offset,
buf_size);
if (ret < 0 && ret != -EAGAIN) {
/* We don't handle any other type of errors here */
abort();
}
if (ret == -EAGAIN || (ret >= 0 && ret < buf_size)) {
/*
* this is a temporary check until chardevs can signal to
* frontends that they are writable again. This prevents
* the console from going into throttled mode (forever)
* if virtio-console is connected to a pty without a
* listener. Otherwise the guest spins forever.
* We can revert this if
* 1: chardevs can notify frondends
* 2: the guest driver does not spin in these cases
*/
if (!vsc->is_console) {
virtio_serial_throttle_port(port, true);
}
if (port->throttled) {
port->iov_idx = i;
if (ret > 0) {
port->iov_offset += ret;