Red Hat Bugzilla – Bug 486291
xm console does not work when xm save fails
Last modified: 2016-04-26 12:41:51 EDT
Description of problem:
When xm save of a PV guest fails, xm console does not accept any input and does not show any output either. However, the guest remains accessible via network, one can ssh to it and no error is shown in guest's logs.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. create a PV guest
2. xm save guest /mnt/small/guest.save # so that it fails
3. xm console
The only thing one can do with the console is disconnecting with Ctrl-]. The console shows no output and accepts no input.
xm console should work as if no xm save command was ever issued
Nothing suspicious is shown in xend.log
Created attachment 340346 [details]
Patch fixing this bug
Created attachment 340500 [details]
Corrected patch fixing this bug
To fix this, new function xc_evtchn_status() has been backported to libxc from current upstream. Using this function, xenconsoled checks status of the event channel associated to the guest and reopens it if necessary.
This patch is backported from upstream staging c/s 19561, which is a modified version of the original patch with some leaks fixed.
Background of this bug: when a guest is resumed after aborted save, the event channel associated to its xenconsole is unbound which prevents xenconsoled from getting or sending any data from/to the guest's console.
Fix built into xen-3.0.3-85.el5
The bug can not be Reproduced in xen-3.0.3-80:
When repeating the following step:
(1)start a paravirtualized guest with 512MB memory
(2)mount a 100MB disk partition on /mnt
# xm save <guest> /mnt/<guest>.save
then save will fail with:
Error: /usr/lib/xen/bin/xc_save 22 5 0 0 0 failed
Usage: xm save <Domain> <CheckpointFile>
Save a domain state to restore later.
domain1 5 511 1 ---s-- 11.3
the guest remains shutdown and can not run again.
The guest remains shutdown. It is not connected via ssh or ping when xm save fails.This is quite like the case in bz 486157.
Repeating the steps above in the system updated to xen-3.0.3-90.el5,the guest still remains shutdown when save failed. xm list shows the guest shutdown.The guest can not start again and can not be connected.
Ah, sorry about that, you would need to reproduce this bug on an older Xen package, for example xen-3.0.3-64.el5. As -80.el5 is affected by a regression https://bugzilla.redhat.com/show_bug.cgi?id=486157.
Also there's no point in trying to verify this bug before successful verification of 486157.
Verified on xen-3.0.3-91.el5
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.