Re: [Xen-devel] Xen-unstable: Bisected Host boot failure on AMD Phenom

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 02/03/17 18:51, Sander Eikelenboom wrote:
> On 02/03/17 19:29, Andrew Cooper wrote:
>> On 02/03/17 18:25, Sander Eikelenboom wrote:
>>> On 02/03/17 18:38, Andrew Cooper wrote:
>>>> On 02/03/17 17:29, Sander Eikelenboom wrote:
>>>>> On 02/03/17 15:55, Andrew Cooper wrote:
>>>>>> On 02/03/17 14:42, Sander Eikelenboom wrote:
>>>>>>> Hi Andrew / Jan,
>>>>>>>
>>>>>>> While testing current xen-unstable staging i ran into my host rebooting 
>>>>>>> in early kernel boot. 
>>>>>>> Bisection has turned up:
>>>>>>>     5cecf60f439e828f4bc0d2a368ced9a73b130cb7 is the first bad commit
>>>>>>>     Author: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>>>>>>>     Date:   Fri Feb 17 17:10:50 2017 +0000
>>>>>>>
>>>>>>>     x86/cpuid: Handle leaf 0x1 in guest_cpuid()
>>>>>>>
>>>>>>> Hardware is a AMD phenom x6.
>>>>>>> Below is the output of serial console of a failed boot.
>>>>>> Hmm.  Sorry for breaking this (although my AMD servers are booting fine).
>>>>> No problem, it is the staging branch of the unstable tree anyway ;-)
>>>>>
>>>>>> It is unfortunately not entirely obvious what Linux is objecting to, and
>>>>>> must be related to something visible in the emulated view.
>>>>>>
>>>>>> Does this delta make any difference?
>>>>> Yes it does, boots fine with this patch applied, thanks !
>>>> That is bad though. :s
>>>>
>>>> It means that something in dom0 has an aversion to my attempt to lie
>>>> less about the topology.
>>>>
>>>> Do you mind checking whether
>>>>
>>>> res->b = cpuid_ebx(0x1) & 0xff00ffffu;
>>>>
>>>> causes is to break again?
>>> Used that in the is_hardware_domain() case and it boots fine.
>> Hmm - curious.  I am now even more confused.
>>
>> What about this?
>>
>> res->b = cpuid_ebx(0x1) & 0x00ffffffu;
>>
>> It will leave the APIC_ID field zeroed rather than feeding v->vcpu_id
>> back into it.
> Also boots fine.

Right.  For my sanity, what about

res->b = cpuid_ebx(0x1) & 0x00ffffffu;
res->b |= (v->vcpu_id * 2) << 24;

?

~Andrew

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