[PATCH 15/17] KVM: arm64: Directly expose mapping prot and kill kvm_s2_fault

[Fuad Tabba]

On Mon, 16 Mar 2026 at 17:55, Marc Zyngier <maz at kernel.org> wrote:
>
> The 'prot' field is the only one left in kvm_s2_fault. Expose it
> directly to the functions needing it, and get rid of kvm_s2_fault.
>
> It has served us well during this refactoring, but it is now no
> longer needed.
>
> Signed-off-by: Marc Zyngier <maz at kernel.org>

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

Cheers,
/fuad


> ---
>  arch/arm64/kvm/mmu.c | 45 +++++++++++++++++++++-----------------------
>  1 file changed, 21 insertions(+), 24 deletions(-)
>
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 97cb3585eba03..9b5df70807875 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1729,10 +1729,6 @@ static short kvm_s2_resolve_vma_size(const struct kvm_s2_fault_desc *s2fd,
>         return vma_shift;
>  }
>
> -struct kvm_s2_fault {
> -       enum kvm_pgtable_prot prot;
> -};
> -
>  static bool kvm_s2_fault_is_perm(const struct kvm_s2_fault_desc *s2fd)
>  {
>         return kvm_vcpu_trap_is_permission_fault(s2fd->vcpu);
> @@ -1856,8 +1852,8 @@ static int kvm_s2_fault_pin_pfn(const struct kvm_s2_fault_desc *s2fd,
>  }
>
>  static int kvm_s2_fault_compute_prot(const struct kvm_s2_fault_desc *s2fd,
> -                                    struct kvm_s2_fault *fault,
> -                                    const struct kvm_s2_fault_vma_info *s2vi)
> +                                    const struct kvm_s2_fault_vma_info *s2vi,
> +                                    enum kvm_pgtable_prot *prot)
>  {
>         struct kvm *kvm = s2fd->vcpu->kvm;
>         bool writable = s2vi->map_writable;
> @@ -1885,23 +1881,25 @@ static int kvm_s2_fault_compute_prot(const struct kvm_s2_fault_desc *s2fd,
>                 return 1;
>         }
>
> +       *prot = KVM_PGTABLE_PROT_R;
> +
>         if (s2fd->nested)
> -               adjust_nested_fault_perms(s2fd->nested, &fault->prot, &writable);
> +               adjust_nested_fault_perms(s2fd->nested, prot, &writable);
>
>         if (writable)
> -               fault->prot |= KVM_PGTABLE_PROT_W;
> +               *prot |= KVM_PGTABLE_PROT_W;
>
>         if (kvm_vcpu_trap_is_exec_fault(s2fd->vcpu))
> -               fault->prot |= KVM_PGTABLE_PROT_X;
> +               *prot |= KVM_PGTABLE_PROT_X;
>
>         if (s2vi->map_non_cacheable)
> -               fault->prot |= (s2vi->vm_flags & VM_ALLOW_ANY_UNCACHED) ?
> -                              KVM_PGTABLE_PROT_NORMAL_NC : KVM_PGTABLE_PROT_DEVICE;
> +               *prot |= (s2vi->vm_flags & VM_ALLOW_ANY_UNCACHED) ?
> +                       KVM_PGTABLE_PROT_NORMAL_NC : KVM_PGTABLE_PROT_DEVICE;
>         else if (cpus_have_final_cap(ARM64_HAS_CACHE_DIC))
> -               fault->prot |= KVM_PGTABLE_PROT_X;
> +               *prot |= KVM_PGTABLE_PROT_X;
>
>         if (s2fd->nested)
> -               adjust_nested_exec_perms(kvm, s2fd->nested, &fault->prot);
> +               adjust_nested_exec_perms(kvm, s2fd->nested, prot);
>
>         if (!kvm_s2_fault_is_perm(s2fd) && !s2vi->map_non_cacheable && kvm_has_mte(kvm)) {
>                 /* Check the VMM hasn't introduced a new disallowed VMA */
> @@ -1913,11 +1911,12 @@ static int kvm_s2_fault_compute_prot(const struct kvm_s2_fault_desc *s2fd,
>  }
>
>  static int kvm_s2_fault_map(const struct kvm_s2_fault_desc *s2fd,
> -                           struct kvm_s2_fault *fault,
> -                           const struct kvm_s2_fault_vma_info *s2vi, void *memcache)
> +                           const struct kvm_s2_fault_vma_info *s2vi,
> +                           enum kvm_pgtable_prot prot,
> +                           void *memcache)
>  {
>         enum kvm_pgtable_walk_flags flags = KVM_PGTABLE_WALK_SHARED;
> -       bool writable = fault->prot & KVM_PGTABLE_PROT_W;
> +       bool writable = prot & KVM_PGTABLE_PROT_W;
>         struct kvm *kvm = s2fd->vcpu->kvm;
>         struct kvm_pgtable *pgt;
>         long perm_fault_granule;
> @@ -1970,12 +1969,12 @@ static int kvm_s2_fault_map(const struct kvm_s2_fault_desc *s2fd,
>                  * Drop the SW bits in favour of those stored in the
>                  * PTE, which will be preserved.
>                  */
> -               fault->prot &= ~KVM_NV_GUEST_MAP_SZ;
> +               prot &= ~KVM_NV_GUEST_MAP_SZ;
>                 ret = KVM_PGT_FN(kvm_pgtable_stage2_relax_perms)(pgt, gfn_to_gpa(gfn),
> -                                                                fault->prot, flags);
> +                                                                prot, flags);
>         } else {
>                 ret = KVM_PGT_FN(kvm_pgtable_stage2_map)(pgt, gfn_to_gpa(gfn), mapping_size,
> -                                                        __pfn_to_phys(pfn), fault->prot,
> +                                                        __pfn_to_phys(pfn), prot,
>                                                          memcache, flags);
>         }
>
> @@ -1999,9 +1998,7 @@ static int user_mem_abort(const struct kvm_s2_fault_desc *s2fd)
>  {
>         bool perm_fault = kvm_vcpu_trap_is_permission_fault(s2fd->vcpu);
>         struct kvm_s2_fault_vma_info s2vi = {};
> -       struct kvm_s2_fault fault = {
> -               .prot = KVM_PGTABLE_PROT_R,
> -       };
> +       enum kvm_pgtable_prot prot;
>         void *memcache;
>         int ret;
>
> @@ -2026,13 +2023,13 @@ static int user_mem_abort(const struct kvm_s2_fault_desc *s2fd)
>         if (ret != 1)
>                 return ret;
>
> -       ret = kvm_s2_fault_compute_prot(s2fd, &fault, &s2vi);
> +       ret = kvm_s2_fault_compute_prot(s2fd, &s2vi, &prot);
>         if (ret) {
>                 kvm_release_page_unused(s2vi.page);
>                 return ret;
>         }
>
> -       return kvm_s2_fault_map(s2fd, &fault, &s2vi, memcache);
> +       return kvm_s2_fault_map(s2fd, &s2vi, prot, memcache);
>  }
>
>  /* Resolve the access fault by making the page young again. */
> --
> 2.47.3
>