Re: [PATCH v3 2/6] KVM: arm64: Handle RASv1p1 registers

[Marc Zyngier <maz@kernel.org>]

On Thu, 21 Aug 2025 14:13:52 +0100,
Ben Horgan <ben.horgan@arm.com> wrote:
> 
> > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> > index 82ffb3b3b3cf7..feb1a7a708e25 100644
> > --- a/arch/arm64/kvm/sys_regs.c
> > +++ b/arch/arm64/kvm/sys_regs.c
> > @@ -2697,6 +2697,18 @@ static bool access_ras(struct kvm_vcpu *vcpu,
> >   	struct kvm *kvm = vcpu->kvm;
> >     	switch(reg_to_encoding(r)) {
> > +	case SYS_ERXPFGCDN_EL1:
> > +	case SYS_ERXPFGCTL_EL1:
> > +	case SYS_ERXPFGF_EL1:
> > +	case SYS_ERXMISC2_EL1:
> > +	case SYS_ERXMISC3_EL1:
> > +		if (!(kvm_has_feat(kvm, ID_AA64PFR0_EL1, RAS, V1P1) ||
> > +		      (kvm_has_feat_enum(kvm, ID_AA64PFR0_EL1, RAS, IMP) &&
> > +		       kvm_has_feat(kvm, ID_AA64PFR1_EL1, RAS_frac, RASv1p1)))) {
> > +			kvm_inject_undefined(vcpu);
> > +			return false;
> > +		}
> > +		break;
> >   	default:
> >   		if (!kvm_has_feat(kvm, ID_AA64PFR0_EL1, RAS, IMP)) {
> >   			kvm_inject_undefined(vcpu);
> The default condition needs updating for the case when
> ID_AA64PFR0_EL1.RAS = b10 otherwise access to the non-v1 specific RAS
> registers will result in an UNDEF being injected.

I don't think so. The RAS field is described as such:

	UnsignedEnum    31:28   RAS
	        0b0000  NI
        	0b0001  IMP
	        0b0010  V1P1
	        0b0011  V2
	EndEnum

Since this is an unsigned enum, this checks for a value < IMP. Only
RAS not being implemented is this condition satisfied, and an UNDEF
injected.

Or am I missing something obvious here (I wouldn't be surprised...)?

	M.

-- 
Jazz isn't dead. It just smells funny.