From 25e6fb590c1986ce0f73499846c50f675ed4e99b Mon Sep 17 00:00:00 2001 From: Amit Shah Date: Mon, 21 Mar 2011 22:06:41 +0100 Subject: [PATCH] virtio-console: Enable port throttling when chardev is slow to consume data When a chardev indicates it can't accept more data, we tell the virtio-serial code to stop sending us any more data till we tell otherwise. This helps in guests continuing to run normally while the vq keeps getting full and eventually the guest stops queueing more data. As soon as the chardev indicates it can accept more data, start pushing! Signed-off-by: Amit Shah Signed-off-by: Cole Robinson --- hw/virtio-console.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/hw/virtio-console.c b/hw/virtio-console.c index 066590c..2b5e515 100644 --- a/hw/virtio-console.c +++ b/hw/virtio-console.c @@ -20,6 +20,16 @@ typedef struct VirtConsole { CharDriverState *chr; } VirtConsole; +/* + * 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); +} /* Callback function that's called when the guest sends us data */ static ssize_t flush_buf(VirtIOSerialPort *port, const uint8_t *buf, size_t len) @@ -110,6 +120,7 @@ static const QemuChrHandlers chr_handlers = { .fd_can_read = chr_can_read, .fd_read = chr_read, .fd_event = chr_event, + .fd_write_unblocked = chr_write_unblocked, }; static int virtconsole_initfn(VirtIOSerialPort *port)