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[Qemu-ppc] [PULL 02/18] pseries: Fix stalls on hypervisor virtual consol

From: Alexander Graf
Subject: [Qemu-ppc] [PULL 02/18] pseries: Fix stalls on hypervisor virtual console
Date: Mon, 2 Sep 2013 10:11:17 +0200

From: Anton Blanchard <address@hidden>

A number of users are reporting stalls when using the pseries
hypervisor virtual console.

A simple test case is to paste 15 or 17 characters at a time
into the console. Pasting 15 characters at a time works fine
but pasting 17 characters hangs for a random amount of time.
Other activity (network, qemu monitor etc) unblocks it.

If qemu-char tries to send more than 16 characters at once,
vty_can_receive returns false. At this point we have to
wait for the guest to consume that output. Everything is good
so far.

The problem occurs when the the guest does consume the output.
We need to signal back to the qemu-char layer that we are
ready for more input. Without this we block until something
else kicks us (eg network activity).

Signed-off-by: Anton Blanchard <address@hidden>
Signed-off-by: Alexander Graf <address@hidden>
 hw/char/spapr_vty.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/hw/char/spapr_vty.c b/hw/char/spapr_vty.c
index a799721..9c2aef8 100644
--- a/hw/char/spapr_vty.c
+++ b/hw/char/spapr_vty.c
@@ -47,6 +47,8 @@ static int vty_getchars(VIOsPAPRDevice *sdev, uint8_t *buf, 
int max)
         buf[n++] = dev->buf[dev->out++ % VTERM_BUFSIZE];
+    qemu_chr_accept_input(dev->chardev);
     return n;

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