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I tried this on a RHEL6 host with new flow control patches and RHEL6 guest.
In the guest, I got:
virtio_console virtio0: control-o:id 0 is not a head!
In the host, I get:
qemu-kvm: virtio-serial-bus: Unexpected port id 478762112 for device virtio-serial-bus.0
qemu-kvm: virtio-serial-bus: Unexpected port id 478762368 for device virtio-serial-bus.0
qemu-kvm: virtio-serial-bus: Unexpected port id 478762112 for device virtio-serial-bus.0
qemu-kvm: virtio-serial-bus: Unexpected port id 478762112 for device virtio-serial-bus.0
qemu-kvm: virtio-serial-bus: Unexpected port id 478762368 for device virtio-serial-bus.0
qemu-kvm: virtio-serial-bus: Unexpected port id 478762368 for device virtio-serial-bus.0
qemu-kvm: virtio-serial-bus: Unexpected port id 478762112 for device virtio-serial-bus.0
qemu-kvm: virtio-serial-bus: Unexpected port id 478762368 for device virtio-serial-bus.0
qemu-kvm: virtio-serial-bus: Unexpected port id 478762368 for device virtio-serial-bus.0
Upstream patches:
commit 165b1b8bbc17c9469b053bab78b11b7cbce6d161
Author: Amit Shah
Date: Fri Mar 29 16:30:07 2013 +0530
virtio: console: rename cvq_lock to c_ivq_lock
The cvq_lock was taken for the c_ivq. Rename the lock to make that
obvious.
We'll also add a lock around the c_ovq in the next commit, so there's no
ambiguity.
commit 9ba5c80b1aea8648a3efe5f22dc1f7cacdfbeeb8
Author: Amit Shah
Date: Fri Mar 29 16:30:08 2013 +0530
virtio: console: add locking around c_ovq operations
When multiple ovq operations are being performed (lots of open/close
operations on virtio_console fds), the __send_control_msg() function can
get confused without locking.
A simple recipe to cause badness is:
* create a QEMU VM with two virtio-serial ports
* in the guest, do
while true;do echo abc >/dev/vport0p1;done
while true;do echo edf >/dev/vport0p2;done
In one run, this caused a panic in __send_control_msg(). In another, I
got
virtio_console virtio0: control-o:id 0 is not a head!
This also results repeated messages similar to these on the host:
qemu-kvm: virtio-serial-bus: Unexpected port id 478762112 for device virtio-serial-bus.0
qemu-kvm: virtio-serial-bus: Unexpected port id 478762368 for device virtio-serial-bus.0
Comment 4RHEL Program Management
2013-04-18 10:40:58 UTC
This request was evaluated by Red Hat Product Management for
inclusion in a Red Hat Enterprise Linux release. Product
Management has requested further review of this request by
Red Hat Engineering, for potential inclusion in a Red Hat
Enterprise Linux release for currently deployed products.
This request is not yet committed for inclusion in a release.
Can reproduce this issue with kernel 2.6.32-358.el6.x86_64(host and guest kernel)
Verify this issue with 2.6.32-394.el6.x86_64
according to steps in comment 0. guest and host work well.
so this bug is fixed.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
http://rhn.redhat.com/errata/RHSA-2013-1645.html