Re: [PATCH] KVM: PPC: Book3S HV: relax check on H_SVM_INIT_ABORT

[Laurent Dufour]

Le 20/05/2020 Ã 19:32, Greg Kurz a ÃcritÂ:
> On Wed, 20 May 2020 18:51:10 +0200
> Laurent Dufour <ldufour@xxxxxxxxxxxxx> wrote:
>
> > The commit 8c47b6ff29e3 ("KVM: PPC: Book3S HV: Check caller of H_SVM_*
> > Hcalls") added checks of secure bit of SRR1 to filter out the Hcall
> > reserved to the Ultravisor.
> >
> > However, the Hcall H_SVM_INIT_ABORT is made by the Ultravisor passing the
> > context of the VM calling UV_ESM. This allows the Hypervisor to return to
> > the guest without going through the Ultravisor. Thus the Secure bit of SRR1
> > is not set in that particular case.
> >
> > In the case a regular VM is calling H_SVM_INIT_ABORT, this hcall will be
> > filtered out in kvmppc_h_svm_init_abort() because kvm->arch.secure_guest is
> > not set in that case.
>
> Why not checking vcpu->kvm->arch.secure_guest then ?

I don't think that's the right place.
> > Fixes: 8c47b6ff29e3 ("KVM: PPC: Book3S HV: Check caller of H_SVM_* Hcalls")
> > Signed-off-by: Laurent Dufour <ldufour@xxxxxxxxxxxxx>
> > ---
> >   arch/powerpc/kvm/book3s_hv.c | 4 +---
> >   1 file changed, 1 insertion(+), 3 deletions(-)
> >
> > diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> > index 93493f0cbfe8..eb1f96cb7b72 100644
> > --- a/arch/powerpc/kvm/book3s_hv.c
> > +++ b/arch/powerpc/kvm/book3s_hv.c
> > @@ -1099,9 +1099,7 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu)
> >   			ret = kvmppc_h_svm_init_done(vcpu->kvm);
> >   		break;
> >   	case H_SVM_INIT_ABORT:
> > -		ret = H_UNSUPPORTED;
> > -		if (kvmppc_get_srr1(vcpu) & MSR_S)
> > -			ret = kvmppc_h_svm_init_abort(vcpu->kvm);
>
> or at least put a comment to explain why H_SVM_INIT_ABORT
> doesn't have the same sanity check as the other SVM hcalls.

I agree that might help. I'll send a v2 with a comment there.

> > +		ret = kvmppc_h_svm_init_abort(vcpu->kvm);
> >   		break;
> >   
> >   	default: