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From 563ef1912e4b0c0b5728bc53d2b225d2ff3cd9ef Mon Sep 17 00:00:00 2001
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From: Amit Shah <amit.shah@redhat.com>
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Date: Mon, 21 Mar 2011 22:06:41 +0100
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Subject: [PATCH] virtio-console: Enable port throttling when chardev is slow
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to consume data
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When a chardev indicates it can't accept more data, we tell the
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virtio-serial code to stop sending us any more data till we tell
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otherwise. This helps in guests continuing to run normally while the vq
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keeps getting full and eventually the guest stops queueing more data.
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As soon as the chardev indicates it can accept more data, start pushing!
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Signed-off-by: Amit Shah <amit.shah@redhat.com>
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Signed-off-by: Cole Robinson <crobinso@redhat.com>
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---
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hw/virtio-console.c | 11 +++++++++++
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1 file changed, 11 insertions(+)
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diff --git a/hw/virtio-console.c b/hw/virtio-console.c
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index dd6f614..0e12514 100644
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--- a/hw/virtio-console.c
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+++ b/hw/virtio-console.c
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@@ -20,6 +20,16 @@ typedef struct VirtConsole {
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CharDriverState *chr;
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} VirtConsole;
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+/*
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+ * Callback function that's called from chardevs when backend becomes
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+ * writable.
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+ */
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+static void chr_write_unblocked(void *opaque)
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+{
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+ VirtConsole *vcon = opaque;
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+
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+ virtio_serial_throttle_port(&vcon->port, false);
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+}
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/* Callback function that's called when the guest sends us data */
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static ssize_t flush_buf(VirtIOSerialPort *port, const uint8_t *buf, size_t len)
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@@ -110,6 +120,7 @@ static const QemuChrHandlers chr_handlers = {
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.fd_can_read = chr_can_read,
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.fd_read = chr_read,
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.fd_event = chr_event,
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+ .fd_write_unblocked = chr_write_unblocked,
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};
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static int virtconsole_initfn(VirtIOSerialPort *port)
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