[PATCH v2 6/6] KVM: arm64: Honor UX/PX attributes for EL2 S1 mappings

[Fuad Tabba]

On Wed, 10 Dec 2025 at 17:30, Marc Zyngier <maz at kernel.org> wrote:
>
> Now that we potentially have two bits to deal with when setting
> execution permissions, make sure we correctly handle them when both
> when building the page tables and when reading back from them.
>
> Reported-by: Alexandru Elisei <alexandru.elisei at arm.com>
> Signed-off-by: Marc Zyngier <maz at kernel.org>

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

/fuad

> ---
>  arch/arm64/include/asm/kvm_pgtable.h | 12 +++---------
>  arch/arm64/kvm/hyp/pgtable.c         | 24 +++++++++++++++++++++---
>  2 files changed, 24 insertions(+), 12 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
> index be68b89692065..095e6b73740a6 100644
> --- a/arch/arm64/include/asm/kvm_pgtable.h
> +++ b/arch/arm64/include/asm/kvm_pgtable.h
> @@ -87,15 +87,9 @@ typedef u64 kvm_pte_t;
>
>  #define KVM_PTE_LEAF_ATTR_HI_SW                GENMASK(58, 55)
>
> -#define __KVM_PTE_LEAF_ATTR_HI_S1_XN   BIT(54)
> -#define __KVM_PTE_LEAF_ATTR_HI_S1_UXN  BIT(54)
> -#define __KVM_PTE_LEAF_ATTR_HI_S1_PXN  BIT(53)
> -
> -#define KVM_PTE_LEAF_ATTR_HI_S1_XN                                     \
> -       ({ cpus_have_final_cap(ARM64_KVM_HVHE) ?                        \
> -                       (__KVM_PTE_LEAF_ATTR_HI_S1_UXN |                \
> -                        __KVM_PTE_LEAF_ATTR_HI_S1_PXN) :               \
> -                       __KVM_PTE_LEAF_ATTR_HI_S1_XN; })
> +#define KVM_PTE_LEAF_ATTR_HI_S1_XN     BIT(54)
> +#define KVM_PTE_LEAF_ATTR_HI_S1_UXN    BIT(54)
> +#define KVM_PTE_LEAF_ATTR_HI_S1_PXN    BIT(53)
>
>  #define KVM_PTE_LEAF_ATTR_HI_S2_XN     GENMASK(54, 53)
>
> diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> index e0bd6a0172729..97c0835d25590 100644
> --- a/arch/arm64/kvm/hyp/pgtable.c
> +++ b/arch/arm64/kvm/hyp/pgtable.c
> @@ -342,6 +342,9 @@ static int hyp_set_prot_attr(enum kvm_pgtable_prot prot, kvm_pte_t *ptep)
>         if (!(prot & KVM_PGTABLE_PROT_R))
>                 return -EINVAL;
>
> +       if (!cpus_have_final_cap(ARM64_KVM_HVHE))
> +               prot &= ~KVM_PGTABLE_PROT_UX;
> +
>         if (prot & KVM_PGTABLE_PROT_X) {
>                 if (prot & KVM_PGTABLE_PROT_W)
>                         return -EINVAL;
> @@ -351,8 +354,16 @@ static int hyp_set_prot_attr(enum kvm_pgtable_prot prot, kvm_pte_t *ptep)
>
>                 if (system_supports_bti_kernel())
>                         attr |= KVM_PTE_LEAF_ATTR_HI_S1_GP;
> +       }
> +
> +       if (cpus_have_final_cap(ARM64_KVM_HVHE)) {
> +               if (!(prot & KVM_PGTABLE_PROT_PX))
> +                       attr |= KVM_PTE_LEAF_ATTR_HI_S1_PXN;
> +               if (!(prot & KVM_PGTABLE_PROT_UX))
> +                       attr |= KVM_PTE_LEAF_ATTR_HI_S1_UXN;
>         } else {
> -               attr |= KVM_PTE_LEAF_ATTR_HI_S1_XN;
> +               if (!(prot & KVM_PGTABLE_PROT_PX))
> +                       attr |= KVM_PTE_LEAF_ATTR_HI_S1_XN;
>         }
>
>         attr |= FIELD_PREP(KVM_PTE_LEAF_ATTR_LO_S1_AP, ap);
> @@ -373,8 +384,15 @@ enum kvm_pgtable_prot kvm_pgtable_hyp_pte_prot(kvm_pte_t pte)
>         if (!kvm_pte_valid(pte))
>                 return prot;
>
> -       if (!(pte & KVM_PTE_LEAF_ATTR_HI_S1_XN))
> -               prot |= KVM_PGTABLE_PROT_X;
> +       if (cpus_have_final_cap(ARM64_KVM_HVHE)) {
> +               if (!(pte & KVM_PTE_LEAF_ATTR_HI_S1_PXN))
> +                       prot |= KVM_PGTABLE_PROT_PX;
> +               if (!(pte & KVM_PTE_LEAF_ATTR_HI_S1_UXN))
> +                       prot |= KVM_PGTABLE_PROT_UX;
> +       } else {
> +               if (!(pte & KVM_PTE_LEAF_ATTR_HI_S1_XN))
> +                       prot |= KVM_PGTABLE_PROT_PX;
> +       }
>
>         ap = FIELD_GET(KVM_PTE_LEAF_ATTR_LO_S1_AP, pte);
>         if (ap == KVM_PTE_LEAF_ATTR_LO_S1_AP_RO)
> --
> 2.47.3
>