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Re: [Xen-users] Issues migrating to xen 4.1

On Sun, Apr 10, 2011 at 12:56:05PM +0800, Sylvain CHEVALIER wrote:
> Hi,
> 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' ].


I replied this 1. in another email.

> 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
> bug?

What do you mean dom0 would stop working? Network dies? 
Does it work from the console? 

And yes, it's recommended to configure networking using the distro
network scripts, see here for examples: 

> 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.

Again what do you mean with dom0 would stop working? dom0 kernel crash? 
hypervisor crash?
And did you mean qemu-dm process in dom0 is leaking memory? 

> 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
> bug?

This definitely sounds like a bug. 

Please set up a serial console and capture the error/crash messages: 

Also: what dom0 kernel version are you using? 

> Any hint or help on finding better solutions would be appreciated

-- Pasi

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