Re: [PATCH v2 06/13] s390x: protvirt: KVM intercept changes

[Cornelia Huck <cohuck@redhat.com>]

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On Thu, 5 Dec 2019 18:34:32 +0100
Janosch Frank <frankja@linux.ibm.com> wrote:

> On 12/5/19 6:15 PM, Cornelia Huck wrote:
> > On Fri, 29 Nov 2019 04:48:02 -0500
> > Janosch Frank <frankja@linux.ibm.com> wrote:
> >   
> >> Secure guests no longer intercept with code 4 for an instruction
> >> interception. Instead they have codes 104 and 108 for secure
> >> instruction interception and secure instruction notification
> >> respectively.
> >>
> >> The 104 mirrors the 4 interception.
> >>
> >> The 108 is a notification interception to let KVM and QEMU know that
> >> something changed and we need to update tracking information or
> >> perform specific tasks. It's currently taken for the following
> >> instructions:
> >>
> >> * stpx (To inform about the changed prefix location)
> >> * sclp (On incorrect SCCB values, so we can inject a IRQ)
> >> * sigp (All but "stop and store status")
> >> * diag308 (Subcodes 0/1)
> >>
> >> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> >> ---
> >>  target/s390x/kvm.c | 6 ++++++
> >>  1 file changed, 6 insertions(+)
> >>

> >> @@ -1664,6 +1668,8 @@ static int handle_intercept(S390CPU *cpu)
> >>              (long)cs->kvm_run->psw_addr);
> >>      switch (icpt_code) {
> >>          case ICPT_INSTRUCTION:
> >> +        case ICPT_PV_INSTR:
> >> +        case ICPT_PV_INSTR_NOTIFICATION:
> >>              r = handle_instruction(cpu, run);  
> > 
> > I'm still a bit uneasy about going through the same path for both 104
> > and 108. How does the handler figure out whether it should emulate an
> > instruction, or just process a notification? Is it guaranteed that a
> > given instruction is always showing up as either a 104 or a 108, so
> > that the handler can check the pv state?  
> 
> diag 308 subcode 0/1 are 108, but all other subcodes are defined as a
> 104 (if they are an exit at all)...

I think that's a reason to really split 108 from 4/104, or at least add
an parameter...

> 
> > 
> > [Even if that works, it still feels a bit unclean to me.]
> >   
> >>              break;
> >>          case ICPT_PROGRAM:  
> > 
> >   
> 
> 


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