[PATCH v4 20/36] KVM: arm64: Disable hierarchical permissions when S1PIE is enabled

[Marc Zyngier]

On Thu, 10 Oct 2024 08:33:13 +0100,
Oliver Upton <oliver.upton at linux.dev> wrote:
> 
> On Wed, Oct 09, 2024 at 08:00:03PM +0100, Marc Zyngier wrote:
> > S1PIE implicitly disables hierarchical permissions, as specified in
> > R_JHSVW, by making TCR_ELx.HPDn RES1.
> > 
> > Add a predicate for S1PIE being enabled for a given translation regime,
> > and emulate this behaviour by forcing the hpd field to true if S1PIE
> > is enabled for that translation regime.
> > 
> > Signed-off-by: Marc Zyngier <maz at kernel.org>
> > ---
> >  arch/arm64/kvm/at.c | 19 +++++++++++++++++++
> >  1 file changed, 19 insertions(+)
> > 
> > diff --git a/arch/arm64/kvm/at.c b/arch/arm64/kvm/at.c
> > index adcfce3f67f03..f5bd750288ff5 100644
> > --- a/arch/arm64/kvm/at.c
> > +++ b/arch/arm64/kvm/at.c
> > @@ -93,6 +93,23 @@ static enum trans_regime compute_translation_regime(struct kvm_vcpu *vcpu, u32 o
> >  	}
> >  }
> >  
> > +static bool s1pie_enabled(struct kvm_vcpu *vcpu, enum trans_regime regime)
> > +{
> > +	if (!kvm_has_feat(vcpu->kvm, ID_AA64MMFR3_EL1, S1PIE, IMP))
> > +		return false;
> > +
> > +	switch (regime) {
> > +	case TR_EL2:
> > +	case TR_EL20:
> > +		return vcpu_read_sys_reg(vcpu, TCR2_EL2) & TCR2_EL2_PIE;
> > +	case TR_EL10:
> > +		return  (__vcpu_sys_reg(vcpu, HCRX_EL2) & HCRX_EL2_TCR2En) &&
> > +			(__vcpu_sys_reg(vcpu, TCR2_EL1) & TCR2_EL1x_PIE);
> > +	default:
> > +		BUG();
> 
> BUILD_BUG()?

Doesn't work. regime is fished out of the walk_info structure, meaning
that it is pretty opaque to the compiler, which in turn needs to emit
code for all cases.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.