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

[David Hildenbrand <david@redhat.com>]

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).

>>
>>> +		sie_page = container_of(scb_s, struct sie_page, sie_block);
>>> +		mcck_info = &sie_page->mcck_info;
>>> +		kvm_s390_reinject_machine_check(vcpu, mcck_info);
>>
>> This could be a simple
>>
>> kvm_s390_reinject_machine_check(vcpu, &vsie_page->mcck_info);
>>
>> no?
> 
> Yes that would be simpler, I guess. Looks like  is just a "do it like the low
> level handler". The code in nmi.c has to go back from the sie control block into
> SIE page. 
> 
> Do you want a respin of this patch?

You can also send a fixup if you don't have to respin.


-- 

Thanks,

David