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

[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?

> >       if (css_general_characteristics.aiv && test_facility(65))
> >           set_kvm_facility(kvm->arch.model.fac_mask, 65);