From 738da364d19bd99b70c79cb1174eef0e19f8e368 Mon Sep 17 00:00:00 2001 From: Amit Shah Date: Mon, 21 Mar 2011 22:06:41 +0100 Subject: [PATCH 108/114] 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 --- 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) -- 1.7.10.4