Re: [kvm-unit-tests PATCH v3 5/6] s390x: lib: sie: don't reenter SIE on pgm int

[Janosch Frank <frankja@linux.ibm.com>]

On 6/30/23 16:59, Nico Boehr wrote:
> Quoting Janosch Frank (2023-06-05 11:30:36)
>> On 6/1/23 09:02, Nico Boehr wrote:
>>> At the moment, when a PGM int occurs while in SIE, we will just reenter
>>> SIE after the interrupt handler was called.
>>>
>>> This is because sie() has a loop which checks icptcode and re-enters SIE
>>> if it is zero.
>>>
>>> However, this behaviour is quite undesirable for SIE tests, since it
>>> doesn't give the host the chance to assert on the PGM int. Instead, we
>>> will just re-enter SIE, on nullifing conditions even causing the
>>> exception again.
>>
>> That's the reason why we set an invalid PGM PSW new for the assembly
>> snippets. Seems like I didn't add it for C snippets for some reason -_-
> 
> True, C snippets should have a invalid PGM new PSW too. Let me have a try after
> my holiday... *writes TODO*
> 
>> This code is fine but it doesn't fully fix the usability aspect and
>> leaves a few questions open:
>>    - Do we want to stick to the code 8 handling?
> 
> Well, I think we need to distinguish between two kinds of PGMs:
> - PGMs in the guest,
> - PGMs caused by SIE on the host (e.g. because the gpa-hpa mapping is not
>    present)
> 
> The first case is out of scope for this patch, but certainly something which can
> be improved.
> 
> This patch focuses on the latter case, where code 8 handling is irrelevant since
> the PGM is always delivered to the host.

Seems like I wasn't fully awake and/or distracted by hunger when I was 
reading this patch -_-