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authorAmit Shah <amit.shah@redhat.com>2014-09-30 21:43:02 +0530
committerPeter Maydell <peter.maydell@linaro.org>2014-10-28 18:35:54 +0000
commit710f292f144ab7a8589ad7c6341356bfeb98dc6c (patch)
tree35231fca36323d22f882e3cb9e2489969ca9ebe0
parent678fe1d2108640569543d42a691e5b8e289ff0ee (diff)
downloadqemu-arm-710f292f144ab7a8589ad7c6341356bfeb98dc6c.tar.gz
virtio: serial: expose a 'guest_writable' callback for users
Users of virtio-serial may want to know when a port becomes writable. A port can stop accepting writes if the guest port is open but not being read from. In this case, data gets queued up in the virtqueue, and after the vq is full, writes to the port do not succeed. When the guest reads off a vq element, and adds a new one for the host to put data in, we can tell users the port is available for more writes, via the new ->guest_writable() callback. Signed-off-by: Amit Shah <amit.shah@redhat.com>
-rw-r--r--hw/char/virtio-serial-bus.c27
-rw-r--r--include/hw/virtio/virtio-serial.h3
2 files changed, 30 insertions, 0 deletions
diff --git a/hw/char/virtio-serial-bus.c b/hw/char/virtio-serial-bus.c
index 3931085983..1c7acbf323 100644
--- a/hw/char/virtio-serial-bus.c
+++ b/hw/char/virtio-serial-bus.c
@@ -465,6 +465,33 @@ static void handle_output(VirtIODevice *vdev, VirtQueue *vq)
static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
{
+ /*
+ * Users of virtio-serial would like to know when guest becomes
+ * writable again -- i.e. if a vq had stuff queued up and the
+ * guest wasn't reading at all, the host would not be able to
+ * write to the vq anymore. Once the guest reads off something,
+ * we can start queueing things up again.
+ */
+ VirtIOSerial *vser;
+ VirtIOSerialPort *port;
+ VirtIOSerialPortClass *vsc;
+
+ vser = VIRTIO_SERIAL(vdev);
+ port = find_port_by_vq(vser, vq);
+
+ if (!port) {
+ return;
+ }
+ vsc = VIRTIO_SERIAL_PORT_GET_CLASS(port);
+
+ /*
+ * If guest_connected is false, this call is being made by the
+ * early-boot queueing up of descriptors, which is just noise for
+ * the host apps -- don't disturb them in that case.
+ */
+ if (port->guest_connected && port->host_connected && vsc->guest_writable) {
+ vsc->guest_writable(port);
+ }
}
static uint32_t get_features(VirtIODevice *vdev, uint32_t features)
diff --git a/include/hw/virtio/virtio-serial.h b/include/hw/virtio/virtio-serial.h
index a679e54aab..b434f78b99 100644
--- a/include/hw/virtio/virtio-serial.h
+++ b/include/hw/virtio/virtio-serial.h
@@ -98,6 +98,9 @@ typedef struct VirtIOSerialPortClass {
/* Guest is now ready to accept data (virtqueues set up). */
void (*guest_ready)(VirtIOSerialPort *port);
+ /* Guest vq became writable again */
+ void (*guest_writable)(VirtIOSerialPort *port);
+
/*
* Guest wrote some data to the port. This data is handed over to
* the app via this callback. The app can return a size less than