[Oneiric] Temporary Xen HVM work-around

Stefan Bader stefan.bader at canonical.com
Thu Sep 1 14:17:03 UTC 2011

On 01.09.2011 16:12, Tim Gardner wrote:
> On 09/01/2011 07:56 AM, Stefan Bader wrote:
>> On 01.09.2011 15:54, Stefan Bader wrote:
>>> On 01.09.2011 15:39, Tim Gardner wrote:
>>>> On 09/01/2011 07:23 AM, Stefan Bader wrote:
>>>>> I would like to propose the following SAUCE patch for Oneiric. Without
>>>>> this the Oneiric kernel fails to boot in HVM mode from a Xen 4.1.1 or
>>>>> newer hypervisor (which we ship in Oneiric).
>>>>> It should be only temporary, but I am not sure we find a proper solution
>>>>> within the time before final freeze and I rather would see the released
>>>>> kernel at least booting.
>>>>> Changes only affect code paths used when booting in HVM mode under Xen,
>>>>> so there should be no other impact.
>>>>> -Stefan
>>>> Can you think of any possible impact this might have for an LTS backport ?
>>>> We're
>>>> not doing anything for -ec2 backports, right ?
>>>> rtg
>>> We do not have an LTS backport for EC2. Of course people can an do run the
>>> normal (generic-pae for i386, amd64 should be ok with any flavour) LTS backport
>>> kernel in Lucid installations. If the hyperviser is older that 4.1.1 this has no
>>> impact at all. And for the other ones it would cause the same issue.
>>> -Stefan
>> Of course I meant "under Xen" somewhere above...
> So if someone was running Lucid user space as a Xen domU guest on a hypervisor
> older then 4.1.1, then installing the Oneiric LTS backport would normally work,
> right? Will this patch impact that ?
> rtg

No, hypervisors older than 4.1.1 will not offer the vector callback feature,
which in turn prevents pv spinlocks (as well as pv IPIs) from being tried to
enable by a 3.0 kernel.
So those work as before.


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