[PATCH v5 21/37] KVM: arm64: Implement AT S1PIE support

[Joey Gouly]

On Wed, Oct 23, 2024 at 03:53:29PM +0100, Marc Zyngier wrote:
> It doesn't take much effort to implement S1PIE support in AT.
> 
> It is only a matter of using the AArch64.S1IndirectBasePermissions()
> encodings for the permission, ignoring GCS which has no impact on AT,
> and enforce FEAT_PAN3 being enabled as this is a requirement of
> FEAT_S1PIE.
> 
> Signed-off-by: Marc Zyngier <maz at kernel.org>
> ---
>  arch/arm64/kvm/at.c | 117 +++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 116 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/at.c b/arch/arm64/kvm/at.c
> index f5bd750288ff5..3d93ed1795603 100644
> --- a/arch/arm64/kvm/at.c
> +++ b/arch/arm64/kvm/at.c
> @@ -781,6 +781,9 @@ static bool pan3_enabled(struct kvm_vcpu *vcpu, enum trans_regime regime)
>  	if (!kvm_has_feat(vcpu->kvm, ID_AA64MMFR1_EL1, PAN, PAN3))
>  		return false;
>  
> +	if (s1pie_enabled(vcpu, regime))
> +		return true;
> +
>  	if (regime == TR_EL10)
>  		sctlr = vcpu_read_sys_reg(vcpu, SCTLR_EL1);
>  	else
> @@ -862,11 +865,123 @@ static void compute_s1_hierarchical_permissions(struct kvm_vcpu *vcpu,
>  	}
>  }
>  
> +#define perm_idx(v, r, i)	((vcpu_read_sys_reg((v), (r)) >> ((i) * 4)) & 0xf)
> +
> +#define set_priv_perms(wr, r, w, x)	\
> +	do {				\
> +		(wr)->pr = (r);		\
> +		(wr)->pw = (w);		\
> +		(wr)->px = (x);		\
> +	} while (0)
> +
> +#define set_unpriv_perms(wr, r, w, x)	\
> +	do {				\
> +		(wr)->ur = (r);		\
> +		(wr)->uw = (w);		\
> +		(wr)->ux = (x);		\
> +	} while (0)
> +
> +/* Similar to AArch64.S1IndirectBasePermissions(), without GCS  */
> +#define set_perms(w, wr, ip)						\
> +	do {								\
> +		/* R_LLZDZ */						\
> +		switch ((ip)) {						\
> +		case 0b0000:						\
> +			set_ ## w ## _perms((wr), false, false, false);	\
> +			break;						\
> +		case 0b0001:						\
> +			set_ ## w ## _perms((wr), true , false, false);	\
> +			break;						\
> +		case 0b0010:						\
> +			set_ ## w ## _perms((wr), false, false, true );	\
> +			break;						\
> +		case 0b0011:						\
> +			set_ ## w ## _perms((wr), true , false, true );	\
> +			break;						\
> +		case 0b0100:						\
> +			set_ ## w ## _perms((wr), false, false, false);	\
> +			break;						\
> +		case 0b0101:						\
> +			set_ ## w ## _perms((wr), true , true , false);	\
> +			break;						\
> +		case 0b0110:						\
> +			set_ ## w ## _perms((wr), true , true , true );	\
> +			break;						\
> +		case 0b0111:						\
> +			set_ ## w ## _perms((wr), true , true , true );	\
> +			break;						\
> +		case 0b1000:						\
> +			set_ ## w ## _perms((wr), true , false, false);	\
> +			break;						\
> +		case 0b1001:						\
> +			set_ ## w ## _perms((wr), true , false, false);	\
> +			break;						\
> +		case 0b1010:						\
> +			set_ ## w ## _perms((wr), true , false, true );	\
> +			break;						\
> +		case 0b1011:						\
> +			set_ ## w ## _perms((wr), false, false, false);	\
> +			break;						\
> +		case 0b1100:						\
> +			set_ ## w ## _perms((wr), true , true , false);	\
> +			break;						\
> +		case 0b1101:						\
> +			set_ ## w ## _perms((wr), false, false, false);	\
> +			break;						\
> +		case 0b1110:						\
> +			set_ ## w ## _perms((wr), true , true , true );	\
> +			break;						\
> +		case 0b1111:						\
> +			set_ ## w ## _perms((wr), false, false, false);	\
> +			break;						\
> +		}							\
> +	} while (0)
> +
> +static void compute_s1_indirect_permissions(struct kvm_vcpu *vcpu,
> +					    struct s1_walk_info *wi,
> +					    struct s1_walk_result *wr)
> +{
> +	u8 up, pp, idx;
> +
> +	idx = pte_pi_index(wr->desc);
> +
> +	switch (wi->regime) {
> +	case TR_EL10:
> +		pp = perm_idx(vcpu, PIR_EL1, idx);
> +		up = perm_idx(vcpu, PIRE0_EL1, idx);
> +		break;
> +	case TR_EL20:
> +		pp = perm_idx(vcpu, PIR_EL2, idx);
> +		up = perm_idx(vcpu, PIRE0_EL2, idx);
> +		break;
> +	case TR_EL2:
> +		pp = perm_idx(vcpu, PIR_EL2, idx);
> +		up = 0;
> +		break;
> +	}

There seems to be inconsistent use of

default:
	BUG();

when switching on wi->regime.

> +
> +	set_perms(priv, wr, pp);
> +
> +	if (wi->regime != TR_EL2)
> +		set_perms(unpriv, wr, up);
> +	else
> +		set_unpriv_perms(wr, false, false, false);

When regime == TR_EL2, up == 0, so the if/else should do the same thing? Maybe
you've done that intentionally to be more explicit.

Either way:

Reviewed-by: Joey Gouly <joey.gouly at arm.com>

> +
> +	/* R_VFPJF */
> +	if (wr->px && wr->uw) {
> +		set_priv_perms(wr, false, false, false);
> +		set_unpriv_perms(wr, false, false, false);
> +	}
> +}
> +
>  static void compute_s1_permissions(struct kvm_vcpu *vcpu, u32 op,
>  				   struct s1_walk_info *wi,
>  				   struct s1_walk_result *wr)
>  {
> -	compute_s1_direct_permissions(vcpu, wi, wr);
> +	if (!s1pie_enabled(vcpu, wi->regime))
> +		compute_s1_direct_permissions(vcpu, wi, wr);
> +	else
> +		compute_s1_indirect_permissions(vcpu, wi, wr);
>  
>  	if (!wi->hpd)
>  		compute_s1_hierarchical_permissions(vcpu, wi, wr);

Thanks,
Joey