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Blame 0108-virtio-console-Enable-port-throttling-when-chardev-i.patch

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From 738da364d19bd99b70c79cb1174eef0e19f8e368 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 108/114] virtio-console: Enable port throttling when chardev
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 is slow 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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---
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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 066590c..2b5e515 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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-- 
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1.7.10.4
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