[PATCH 05/17] KVM: arm64: Constrain fault_granule to kvm_s2_fault_map()

[Fuad Tabba]

On Mon, 16 Mar 2026 at 17:55, Marc Zyngier <maz at kernel.org> wrote:
>
> The notion of fault_granule is specific to kvm_s2_fault_map(), and
> is unused anywhere else.
>
> Move this variable locally, removing it from kvm_s2_fault.
>
> Signed-off-by: Marc Zyngier <maz at kernel.org>

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

Cheers,
/fuad
> ---
>  arch/arm64/kvm/mmu.c | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 1b32f2e6c3e61..12c2f0aeaae4c 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1724,7 +1724,6 @@ struct kvm_s2_fault {
>         bool logging_active;
>         bool force_pte;
>         long vma_pagesize;
> -       long fault_granule;
>         enum kvm_pgtable_prot prot;
>         struct page *page;
>         vm_flags_t vm_flags;
> @@ -1908,9 +1907,9 @@ static phys_addr_t get_ipa(const struct kvm_s2_fault *fault)
>  static int kvm_s2_fault_map(const struct kvm_s2_fault_desc *s2fd,
>                             struct kvm_s2_fault *fault, void *memcache)
>  {
> -       bool fault_is_perm = kvm_s2_fault_is_perm(s2fd);
>         struct kvm *kvm = s2fd->vcpu->kvm;
>         struct kvm_pgtable *pgt;
> +       long perm_fault_granule;
>         int ret;
>         enum kvm_pgtable_walk_flags flags = KVM_PGTABLE_WALK_SHARED;
>
> @@ -1920,14 +1919,17 @@ static int kvm_s2_fault_map(const struct kvm_s2_fault_desc *s2fd,
>         if (mmu_invalidate_retry(kvm, fault->mmu_seq))
>                 goto out_unlock;
>
> +       perm_fault_granule = (kvm_s2_fault_is_perm(s2fd) ?
> +                             kvm_vcpu_trap_get_perm_fault_granule(s2fd->vcpu) : 0);
> +
>         /*
>          * If we are not forced to use fault->page mapping, check if we are
>          * backed by a THP and thus use block mapping if possible.
>          */
>         if (fault->vma_pagesize == PAGE_SIZE &&
>             !(fault->force_pte || fault->s2_force_noncacheable)) {
> -               if (fault_is_perm && fault->fault_granule > PAGE_SIZE) {
> -                       fault->vma_pagesize = fault->fault_granule;
> +               if (perm_fault_granule > PAGE_SIZE) {
> +                       fault->vma_pagesize = perm_fault_granule;
>                 } else {
>                         fault->vma_pagesize = transparent_hugepage_adjust(kvm, s2fd->memslot,
>                                                                           s2fd->hva, &fault->pfn,
> @@ -1940,15 +1942,15 @@ static int kvm_s2_fault_map(const struct kvm_s2_fault_desc *s2fd,
>                 }
>         }
>
> -       if (!fault_is_perm && !fault->s2_force_noncacheable && kvm_has_mte(kvm))
> +       if (!perm_fault_granule && !fault->s2_force_noncacheable && kvm_has_mte(kvm))
>                 sanitise_mte_tags(kvm, fault->pfn, fault->vma_pagesize);
>
>         /*
>          * Under the premise of getting a FSC_PERM fault, we just need to relax
> -        * permissions only if fault->vma_pagesize equals fault->fault_granule. Otherwise,
> +        * permissions only if vma_pagesize equals perm_fault_granule. Otherwise,
>          * kvm_pgtable_stage2_map() should be called to change block size.
>          */
> -       if (fault_is_perm && fault->vma_pagesize == fault->fault_granule) {
> +       if (fault->vma_pagesize == perm_fault_granule) {
>                 /*
>                  * Drop the SW bits in favour of those stored in the
>                  * PTE, which will be preserved.
> @@ -1984,7 +1986,6 @@ static int user_mem_abort(const struct kvm_s2_fault_desc *s2fd)
>                 .logging_active = logging_active,
>                 .force_pte = logging_active,
>                 .prot = KVM_PGTABLE_PROT_R,
> -               .fault_granule = perm_fault ? kvm_vcpu_trap_get_perm_fault_granule(s2fd->vcpu) : 0,
>                 .write_fault = write_fault,
>                 .exec_fault = kvm_vcpu_trap_is_exec_fault(s2fd->vcpu),
>                 .topup_memcache = !perm_fault || (logging_active && write_fault),
> --
> 2.47.3
>