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

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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 -_-




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