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Fix fedora guest hang with virtio console (bz 837925)

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This commit is contained in:
Cole Robinson 2012-07-18 18:01:46 -04:00
parent 45f96fecc4
commit 9e4ae06b20
2 changed files with 54 additions and 1 deletions
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47
qemu-virtio-console-unconnected-pty.patch Normal file
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@ -0,0 +1,47 @@
commit ed8e5a85a1741147ce06932b478a509ce3407061
Author: Christian Borntraeger <borntraeger@de.ibm.com>
Date: Thu Dec 29 13:47:43 2011 +0100
virtio-console: Fix failure on unconnected pty
when I tried qemu with -virtio-console pty the guest hangs and attaching
on /dev/pts/<x> does not return anything if the attachment is too late.
This results in pty_chr_write() returning 0, which causes the port to
get throttled. This results in the guest getting frozen as the
guest->host virtio_console writes don't return until the host releases
the vq element back to the guest.
For the virtio-serial use case we don't want to lose data but for the
console case we better drop data instead of "killing" the guest
console. If we get chardev->frontend notification and a better behaving
virtio-console we can revert this fix.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
diff --git a/hw/virtio-serial-bus.c b/hw/virtio-serial-bus.c
index fe0233f..3a9004a 100644
--- a/hw/virtio-serial-bus.c
+++ b/hw/virtio-serial-bus.c
@@ -163,7 +163,19 @@ static void do_flush_queued_data(VirtIOSerialPort *port, VirtQueue *vq,
abort();
}
if (ret == -EAGAIN || (ret >= 0 && ret < buf_size)) {
- virtio_serial_throttle_port(port, true);
+ /*
+ * this is a temporary check until chardevs can signal to
+ * frontends that they are writable again. This prevents
+ * the console from going into throttled mode (forever)
+ * if virtio-console is connected to a pty without a
+ * listener. Otherwise the guest spins forever.
+ * We can revert this if
+ * 1: chardevs can notify frondends
+ * 2: the guest driver does not spin in these cases
+ */
+ if (!info->is_console) {
+ virtio_serial_throttle_port(port, true);
+ }
port->iov_idx = i;
if (ret > 0) {
port->iov_offset += ret;

8
qemu.spec
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@ -38,7 +38,7 @@
Summary: QEMU is a FAST! processor emulator
Name: qemu
Version: 1.0
Release: 17%{?dist}
Release: 18%{?dist}
# Epoch because we pushed a qemu-1.0 package
Epoch: 2
License: GPLv2+ and LGPLv2+ and BSD
@ -207,6 +207,8 @@ Patch506: 0506-audio-spice-add-support-for-volume-control.patch
Patch507: 0507-Do-not-use-pa_simple-PulseAudio-API.patch
Patch508: 0508-configure-pa_simple-is-not-needed-anymore.patch
Patch509: 0509-Allow-controlling-volume-with-PulseAudio-backend.patch
# Fix fedora guest hang with virtio console (bz 837925)
Patch510: %{name}-virtio-console-unconnected-pty.patch
BuildRoot: %{_tmppath}/%{name}-%{version}-%{release}-root-%(%{__id_u} -n)
BuildRequires: SDL-devel zlib-devel which texi2html gnutls-devel cyrus-sasl-devel
@ -578,6 +580,7 @@ such as kvm_stat.
%patch507 -p1
%patch508 -p1
%patch509 -p1
%patch510 -p1
%build
@ -1009,6 +1012,9 @@ fi
%{_mandir}/man1/qemu-img.1*
%changelog
* Wed Jul 18 2012 Cole Robinson <crobinso@redhat.com> - 1.0-18
- Fix fedora guest hang with virtio console (bz 837925)
* Mon Apr 23 2012 Paolo Bonzini <pbonzini@redhat.com> - 2:1.0-17
- Fix install failure due to set -e (rhbz #815272)