Re: [Xen-users] pvhvm on debian

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Sun, 2012-09-09 at 21:23 +0100, chris wrote:
> So as you can see the domU is identical kernel in both cases however
> when the domU is running on the wheezy dom0 even despite that the
> platform pci device appears exactly the same in lspci 

Is the contents of the initrd identical in both cases? Specifically do
they both contain the same set of kernel modules?

Note that CentOS does not strictly speaking contain "PVHVM", which is a
more recent upstream development. What you have here is the PV drivers
add on driver from the unmodified_drivers. Did these drivers ship with
CentOS or did you get them from elsewhere? Do you have the source for
them?

The difference is that PVHVM is part of the kernel itself and are
tightly integrated, while the unmodified_drivers are a set of drivers
used as an "add-on" pack for various existing OSes (similar in principal
to how e.g. the Windows drivers are supplied for Windows). The main
differences in practice will be at setup and initialisation time, which
of course is where things appear to be going wrong for you.

I think this highlights why it is important to always give all the
precise details in a bug report, this is the first time CentOS has been
mentioned at all so I think I can be forgiven for assuming you were
running Debian PVHVM in the guest too (which is what I spent time
reproducing).

> I've attached the configs and logs that you asked for

I asked for guest console logs. The guest console logs are where the
guest decisions about PVHVM drivers will be logged, if anywhere.

sektor-qemu.txt and baraka-qemu.txt are identical, but they both contain
references to "baraka" which should surely be "sektor" in the at least
one place (e.g. the disk path) for that VM.

Your vm configs show the name has changed in the disk path so I don't
see why it isn't different in the logs too. re you sure these are the
actual logs from real runs of the guest?

> Any ideas how to debug further? The difference between the working
> scenario and nonworking is the dom0 distro (squeeze vs wheezy), dom0
> kernel and dom0 hypervisor
> Testing with both scenario's was done with the exact same domU so I
> cant see how it could be a domU issue.

Comparing your guest configs shows that they aren't actual quite
identical though, for reasons other than the different names.

One has apic=1 then other doesn't, I'm not sure what the default is, and
also one names its vif with vifname and the other doesn't.

Perhaps these don't matter but it suggests that you need to double check
your assumption that these VMs are "identical".

Ian.




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