[Oneiric] Temporary Xen HVM work-around

[Tim Gardner]

On 09/01/2011 08:17 AM, Stefan Bader wrote:
> 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.
>
> -Stefan

Uh, I think what you just said is that Oneiric will work fine on 
hypervisors prior to 4.1.1 regardless of whether this patch is applied.

rtg
-- 
Tim Gardner tim.gardner at canonical.com