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

[Cornelia Huck]

On Fri, 6 Dec 2019 08:44:52 +0100
Janosch Frank <address@hidden> wrote:

> On 12/5/19 6:46 PM, Cornelia Huck wrote:
> > On Thu, 5 Dec 2019 18:34:32 +0100
> > Janosch Frank <address@hidden> wrote:
> >   
> >> On 12/5/19 6:15 PM, Cornelia Huck wrote:  
> >>> On Fri, 29 Nov 2019 04:48:02 -0500
> >>> Janosch Frank <address@hidden> 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 <address@hidden>
> >>>> ---
> >>>>  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...  
> 
> And still call the diag 308 handler or have separate handlers?

I'd probably split it into a "normal" one and one for pv special
handling... does that make sense?

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