Re: [Xen-devel] Xen 4.8 + Linux 4.9 + Credit2 = can't bootup

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 01/12/2017 07:50 AM, Dario Faggioli wrote:
> On Wed, 2017-01-04 at 22:13 -0500, Boris Ostrovsky wrote:
>> On 01/04/2017 09:10 PM, Konrad Rzeszutek Wilk wrote:
>>> On Wed, Jan 04, 2017 at 08:52:03PM -0500, Konrad Rzeszutek Wilk
>>> wrote:
>>>> I was trying to bootup on an 30 CPU machine (15 core, SMT).
>>>>
>>>> It works just fine with credit1 (see further down the log)
>>>> but if I try credit2 it ends up hanging during bootup.
>>>>
>>>> I am a going to naively assume it is due to how the vCPUs are
>>>> exposed (Where they match the physical CPUs under credit1),
>>>> but under credit2 they are different.
>>> It seems now that I took dom0_max_vcpus out of the picture I can
>>> reproduce this with credit1 scheduler. So it looks like an Linux
>>> issue.
>>>
>>> Boris, any ideas? This is 4.9.
>>>
>> I think 4.9 is broken. There were changes in topology initialization 
>> that broke Xen in early 4.9 RCs. 
>>
> Maybe it's me misremembering/saying stupid things, but I recall that at
> some point we were testing some of the recent and in development Linux
> branches in OSSTest.
>
> I don't think we do that any longer, and that may be part of the reason
> why we missed this one?

I believe you needed to be on a multi-socket system to catch this bug.
That's why, for example, my tests missed it --- the boxes that I use are
all single-node.

-boris

>
> Ian, Wei, thoughts?
>
> Regards,
> Dario

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