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[Xen-users] Issues migrating to xen 4.1

  • To: xen-users@xxxxxxxxxxxxxxxxxxx
  • From: Sylvain CHEVALIER <sylvain.chevalier@xxxxxxxxx>
  • Date: Sun, 10 Apr 2011 12:56:05 +0800
  • Delivery-date: Sat, 09 Apr 2011 21:57:52 -0700
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We just migrated xen on gentoo on amd64 from 4.0 to 4.1 and
encountered a few issues that were not documented. Here is how we
solved them and what issues are remaining:

1. Our config files were referring to the LVM devices like
/dev/vg/domU-root with disk = [ 'phy:vg/domU-root,sda1,w' ]. This does
not work anymore, we have to include '/dev/': disk = [
'phy:/dev/vg/domU-root,sda1,w' ].

2. We were using bridges to map the 4 ethernet cards to virtual
machines so that virtual machines could have their own IP addresses.
In xen 4.1, it is recommended to configure bridges by ourselves and
not use xend although xend would still work. We could not get the
bridges to work and went on using xend. However, the network-bridge
script now includes a test: if a bridge already exist, then it would
do nothing. The problem with that is that our wrapper script for
network-bridge would only create the first bridge. So we had to
comment out the test in network-bridge, and it would work. Did anybody
successfully create bridges on gentoo?
Meanwhile, we found that if a domU is started and tries to access a
bridge that does not exist, dom0 would stop working. Shall it be a

3. I believe we have memory issues when running a windows domU. We use
to allocate 512MB to domU and found that qemu would quickly use most
of it and after a while, dom0 would stop working. Now we allocate 4GB,
made sure there is no ballooning and it appears to work fine. Memory
leaks by qemu are widely reported but I wonder why we did not have
such issues before xen 4.1 update.

4. We might also have issues with CPUs. dom0 and all domU were
authorized to use all CPUs, and we saw the whole system freezing often
and quickly when mounting in charge after the 4.1 update. After we
spinned one CPU to dom0 we haven't seen this issue. Would this be a

Any hint or help on finding better solutions would be appreciated



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