[PATCH 11/20] KVM: arm64: Add REQUIRES_E2H1 constraint as configuration flags

[Fuad Tabba]

On Mon, 26 Jan 2026 at 12:17, Marc Zyngier <maz at kernel.org> wrote:
>
> A bunch of EL2 configuration are very similar to their EL1 counterpart,
> with the added constraint that HCR_EL2.E2H being 1.
>
> For us, this means HCR_EL2.E2H being RES1, which is something we can
> statically evaluate.
>
> Add a REQUIRES_E2H1 constraint, which allows us to express conditions
> in a much simpler way (without extra code). Existing occurrences are
> converted, before we add a lot more.
>
> Signed-off-by: Marc Zyngier <maz at kernel.org>
> ---
>  arch/arm64/kvm/config.c | 38 ++++++++++++++------------------------
>  1 file changed, 14 insertions(+), 24 deletions(-)
>
> diff --git a/arch/arm64/kvm/config.c b/arch/arm64/kvm/config.c
> index 4fac04d3132c0..1990cebc77c66 100644
> --- a/arch/arm64/kvm/config.c
> +++ b/arch/arm64/kvm/config.c
> @@ -25,6 +25,7 @@ struct reg_bits_to_feat_map {
>  #define        FIXED_VALUE     BIT(2)  /* RAZ/WI or RAO/WI in KVM */
>  #define        MASKS_POINTER   BIT(3)  /* Pointer to fgt_masks struct instead of bits */
>  #define        AS_RES1         BIT(4)  /* RES1 when not supported */
> +#define        REQUIRES_E2H1   BIT(5)  /* Add HCR_EL2.E2H RES1 as a pre-condition */
>
>         unsigned long   flags;
>
> @@ -311,21 +312,6 @@ static bool feat_trbe_mpam(struct kvm *kvm)
>                 (read_sysreg_s(SYS_TRBIDR_EL1) & TRBIDR_EL1_MPAM));
>  }
>
> -static bool feat_asid2_e2h1(struct kvm *kvm)
> -{
> -       return kvm_has_feat(kvm, FEAT_ASID2) && !kvm_has_feat(kvm, FEAT_E2H0);
> -}
> -
> -static bool feat_d128_e2h1(struct kvm *kvm)
> -{
> -       return kvm_has_feat(kvm, FEAT_D128) && !kvm_has_feat(kvm, FEAT_E2H0);
> -}
> -
> -static bool feat_mec_e2h1(struct kvm *kvm)
> -{
> -       return kvm_has_feat(kvm, FEAT_MEC) && !kvm_has_feat(kvm, FEAT_E2H0);
> -}
> -
>  static bool feat_ebep_pmuv3_ss(struct kvm *kvm)
>  {
>         return kvm_has_feat(kvm, FEAT_EBEP) || kvm_has_feat(kvm, FEAT_PMUv3_SS);
> @@ -1045,15 +1031,15 @@ static const DECLARE_FEAT_MAP(sctlr2_desc, SCTLR2_EL1,
>                               sctlr2_feat_map, FEAT_SCTLR2);
>
>  static const struct reg_bits_to_feat_map tcr2_el2_feat_map[] = {
> -       NEEDS_FEAT(TCR2_EL2_FNG1        |
> -                  TCR2_EL2_FNG0        |
> -                  TCR2_EL2_A2,
> -                  feat_asid2_e2h1),
> -       NEEDS_FEAT(TCR2_EL2_DisCH1      |
> -                  TCR2_EL2_DisCH0      |
> -                  TCR2_EL2_D128,
> -                  feat_d128_e2h1),
> -       NEEDS_FEAT(TCR2_EL2_AMEC1, feat_mec_e2h1),
> +       NEEDS_FEAT_FLAG(TCR2_EL2_FNG1   |
> +                       TCR2_EL2_FNG0   |
> +                       TCR2_EL2_A2,
> +                       REQUIRES_E2H1, FEAT_ASID2),
> +       NEEDS_FEAT_FLAG(TCR2_EL2_DisCH1 |
> +                       TCR2_EL2_DisCH0 |
> +                       TCR2_EL2_D128,
> +                       REQUIRES_E2H1, FEAT_D128),
> +       NEEDS_FEAT_FLAG(TCR2_EL2_AMEC1, REQUIRES_E2H1, FEAT_MEC),
>         NEEDS_FEAT(TCR2_EL2_AMEC0, FEAT_MEC),
>         NEEDS_FEAT(TCR2_EL2_HAFT, FEAT_HAFT),
>         NEEDS_FEAT(TCR2_EL2_PTTWI       |
> @@ -1285,6 +1271,7 @@ struct resx compute_resx_bits(struct kvm *kvm,
>                               unsigned long require,
>                               unsigned long exclude)
>  {
> +       bool e2h0 = kvm_has_feat(kvm, FEAT_E2H0);
>         struct resx resx = {};
>
>         for (int i = 0; i < map_size; i++) {
> @@ -1307,6 +1294,9 @@ struct resx compute_resx_bits(struct kvm *kvm,
>                         match = idreg_feat_match(kvm, &map[i]);
>                 }
>
> +               if (map[i].flags & REQUIRES_E2H1)
> +                       match &= !e2h0;
> +

nit: white space in the newline

Reviewed-by: Fuad Tabba <tabba at google.com>

Cheers,
/fuad




>                 if (!match) {
>                         if (map[i].flags & AS_RES1)
>                                 resx.res1 |= reg_feat_map_bits(&map[i]);
> --
> 2.47.3
>