/* Callback function that's called when the guest sends us data */
static ssize_t flush_buf(VirtIOSerialPort *port,
const uint8_t *buf, ssize_t len)
{
VirtConsole *vcon = DO_UPCAST(VirtConsole, port, port);
ssize_t ret;
if (!vcon->chr) {
/* If there's no backend, we can just say we consumed all data. */
return len;
}
ret = qemu_chr_fe_write(vcon->chr, buf, len);
trace_virtio_console_flush_buf(port->id, len, ret);
if (ret < len) {
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.
*/
if (ret < 0)
ret = 0;
if (!k->is_console) {
virtio_serial_throttle_port(port, true);
if (!vcon->watch) {
vcon->watch = qemu_chr_fe_add_watch(vcon->chr, G_IO_OUT,
chr_write_unblocked, vcon);
}
}
}
return ret;
}
/* Callback function that's called when the guest sends us data */
static ssize_t flush_buf(VirtIOSerialPort *port,
const uint8_t *buf, ssize_t len)
{
VirtConsole *vcon = VIRTIO_CONSOLE(port);
ssize_t ret;
if (!qemu_chr_fe_backend_connected(&vcon->chr)) {
/* If there's no backend, we can just say we consumed all data. */
return len;
}
ret = qemu_chr_fe_write(&vcon->chr, buf, len);
trace_virtio_console_flush_buf(port->id, len, ret);
if (ret < len) {
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.
*/
if (ret < 0)
ret = 0;
/* XXX we should be queuing data to send later for the
* console devices too rather than silently dropping
* console data on EAGAIN. The Linux virtio-console
* hvc driver though does sends with spinlocks held,
* so if we enable throttling that'll stall the entire
* guest kernel, not merely the process writing to the
* console.
*
* While we could queue data for later write without
* enabling throttling, this would result in the guest
* being able to trigger arbitrary memory usage in QEMU
* buffering data for later writes.
*
* So fixing this problem likely requires fixing the
* Linux virtio-console hvc driver to not hold spinlocks
* while writing, and instead merely block the process
* that's writing. QEMU would then need some way to detect
* if the guest had the fixed driver too, before we can
* use throttling on host side.
*/
if (!k->is_console) {
virtio_serial_throttle_port(port, true);
if (!vcon->watch) {
vcon->watch = qemu_chr_fe_add_watch(&vcon->chr,
G_IO_OUT|G_IO_HUP,
chr_write_unblocked, vcon);
}
}
}
return ret;
}
/*
* Callback function that's called from chardevs when backend becomes
* writable.
*/
static gboolean chr_write_unblocked(GIOChannel *chan, GIOCondition cond,
void *opaque)
{
VirtConsole *vcon = opaque;
vcon->watch = 0;
virtio_serial_throttle_port(VIRTIO_SERIAL_PORT(vcon), false);
return FALSE;
}
static void vmc_have_data(VirtIOSerialPort *port, const uint8_t *buf, size_t len)
{
SpiceVirtualChannel *svc = DO_UPCAST(SpiceVirtualChannel, port, port);
dprintf(svc, 2, "%s: %zd\n", __func__, len);
assert(svc->datalen == 0);
if (svc->bufsize < len) {
svc->bufsize = len;
svc->buffer = qemu_realloc(svc->buffer, svc->bufsize);
}
memcpy(svc->buffer, buf, len);
svc->datapos = svc->buffer;
svc->datalen = len;
virtio_serial_throttle_port(&svc->port, true);
spice_server_char_device_wakeup(&svc->sin);
}
static int vmc_read(SpiceCharDeviceInstance *sin, uint8_t *buf, int len)
{
SpiceVirtualChannel *svc = container_of(sin, SpiceVirtualChannel, sin);
int bytes = MIN(len, svc->datalen);
dprintf(svc, 2, "%s: %p %d/%d/%zd\n", __func__, svc->datapos, len, bytes, svc->datalen);
if (bytes > 0) {
memcpy(buf, svc->datapos, bytes);
svc->datapos += bytes;
svc->datalen -= bytes;
assert(svc->datalen >= 0);
if (svc->datalen == 0) {
svc->datapos = 0;
virtio_serial_throttle_port(&svc->port, false);
// ^^^ !!! may call vmc_have_data, so don't touch svc after it!
}
}
return bytes;
}
/*
* Callback function that's called from chardevs when backend becomes
* writable.
*/
static void chr_write_unblocked(void *opaque)
{
VirtConsole *vcon = opaque;
virtio_serial_throttle_port(&vcon->port, false);
}
