Re: [PATCH 16/32] KVM: s390: expose the guest zPCI interpretation facility

[Matthew Rosato]

On 12/17/21 11:58 AM, Christian Borntraeger wrote:
> Am 17.12.21 um 16:19 schrieb Matthew Rosato:
> > On 12/17/21 10:05 AM, Christian Borntraeger wrote:
> > > Am 07.12.21 um 21:57 schrieb Matthew Rosato:
> > > > This facility will be used to enable interpretive execution of zPCI
> > > > instructions.
> > > >
> > > > Signed-off-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx>
> > > > ---
> > > >   arch/s390/kvm/kvm-s390.c | 4 ++++
> > > >   1 file changed, 4 insertions(+)
> > > >
> > > > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> > > > index c8fe9b7c2395..09991d05c871 100644
> > > > --- a/arch/s390/kvm/kvm-s390.c
> > > > +++ b/arch/s390/kvm/kvm-s390.c
> > > > @@ -2751,6 +2751,10 @@ int kvm_arch_init_vm(struct kvm *kvm, 
> > > > unsigned long type)
> > > >           set_kvm_facility(kvm->arch.model.fac_mask, 147);
> > > >           set_kvm_facility(kvm->arch.model.fac_list, 147);
> > > >       }
> > > > +    if (sclp.has_zpci_interp && test_facility(69)) {
> > > > +        set_kvm_facility(kvm->arch.model.fac_mask, 69);
> > > > +        set_kvm_facility(kvm->arch.model.fac_list, 69);
> > > > +    }
> > >
> > >
> > > Do we need the setting of these stfle bits somewhere? I think QEMU 
> > > sets them as well for the guest. > We only need this when the kernel 
> > > probes for this (test_kvm_facility)
> > > But then the question is, shouldnt
> > > we then simply check for sclp bits in those places?
> > > See also patch 19. We need to build it in a way that allows VSIE 
> > > support later on.
> >
> > Right, so this currently sets the facility bits but we don't set the 
> > associated guest SCLP bits.  I guess since we are not enabling for 
> > VSIE now it would make sense to not set either.
> >
> > So then just to confirm we are on the same page:  I will drop these 
> > patches 16-18 and leave the kvm facilities unset until we wish to 
> > enable VSIE.  And then also make sure we are checking sclp bits (e.g. 
> > patch 19).  OK?
>
> Right drop these patches and change patch 19. When we later enable VSIE 
> we need QEMU to set the sclp bits. Not sure, does this work as of today 
> or do we need additional vsie changes (I would assume so)?

No, we will need some additional work to be able to enable for VSIE 
(e.g. adapter interrupt source ID)