Re: [GIT PULL 9/9] KVM: s390: Inject machine check into the nested guest

[David Hildenbrand <david@redhat.com>]

On 29.06.2017 16:57, Christian Borntraeger wrote:
> On 06/28/2017 09:16 PM, Christian Borntraeger wrote:
>> On 06/28/2017 09:08 PM, David Hildenbrand wrote:
>>> On 28.06.2017 20:59, Christian Borntraeger wrote:
>>>> On 06/28/2017 08:06 PM, David Hildenbrand wrote:
>>>>> On 28.06.2017 19:30, Christian Borntraeger wrote:
>>>>>> From: QingFeng Hao <haoqf@linux.vnet.ibm.com>
>>>>>>
>>>>>> With vsie feature enabled, kvm can support nested guests (guest-3).
>>>>>> So inject machine check to the guest-2 if it happens when the nested
>>>>>> guest is running. And guest-2 will detect the machine check belongs
>>>>>> to guest-3 and reinject it into guest-3.
>>>>>> The host (guest-1) tries to inject the machine check to the picked
>>>>>> destination vcpu if it's a floating machine check.
>>>>>
>>>>> The subject is confusing. We don't inject anything into the nested guest
>>>>> here. We just catch machine checks during vsie and inject it into the
>>>>> ordinary kvm guest.
>>>>
>>>> Agreed, it is confusing and maybe a leftover from an early rework due to internal
>>>> feedback. We inject in guest-2 and rely on guest-2 to reinject to guest-3 would
>>>> be a better wording.
>>>>
>>>>  
>>>>
>>>>
>>>>> Are there any SIE specific things to consider here, that may have to be
>>>>> translated?
>>>>
>>>> As HW exits SIE before delivering the machine check, the SIE control block 
>>>> contains all saved guest3 registers and the host (guest1) registers contain
>>>> the lazy registers (as we have already restored them) just like a normal exit.
>>>
>>> As mentioned in the other mail, e.g. vector register validity should
>>> only be set if vector registers are enabled for the nested guest
>>> (execution control enabled).
>>
>> Yes, but sInce we inject in the base guest (non-nested) we have to check the base guest
>> execution control. 
> 
> While we drag the vector validity along, it looks like __write_machine_check is already
> doing the right thing for vector and guarded storage before writing the mcic to the
> guest, no?

(sorry for the delay, I'm currently visiting a rural part of Slovakia)

Yes, perfect. So the only thing that could actually happen is an under
indication, which can be easily added later.

Thanks!


-- 

Thanks,

David