From 71108acb189f5fda923013ed72270642199ab50d Mon Sep 17 00:00:00 2001 From: Amit Shah Date: Mon, 21 Mar 2011 22:06:41 +0100 Subject: [PATCH 113/118] 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 files changed, 11 insertions(+), 0 deletions(-) diff --git a/hw/virtio-console.c b/hw/virtio-console.c index 6d6f3ef..da68211 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) @@ -99,6 +109,7 @@ 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) -- 1.7.7.5