APPLIED: [Oneiric] Temporary Xen HVM work-around

[Tim Gardner]

On 09/01/2011 08:37 AM, Stefan Bader wrote:
> On 01.09.2011 16:25, Tim Gardner wrote:
>> 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
>
> Yes.
>
> -Stefan


-- 
Tim Gardner tim.gardner at canonical.com