[PATCH 13/17] KVM: arm64: Replace force_pte with a max_map_size attribute

[Fuad Tabba]

On Mon, 16 Mar 2026 at 17:55, Marc Zyngier <maz at kernel.org> wrote:
>
> force_pte is annoyingly limited in what it expresses, and we'd
> be better off with a more generic primitive. Introduce max_map_size
> instead, which does the trick and can be moved into the vma_info
> structure. This firther allows it to reduce the scopes in which

nit: firther -> further

> it is mutable.
>
> Signed-off-by: Marc Zyngier <maz at kernel.org>


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

Cheers,
/fuad


> ---
>  arch/arm64/kvm/mmu.c | 47 +++++++++++++++++++++++---------------------
>  1 file changed, 25 insertions(+), 22 deletions(-)
>
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index ccdc9398e4ce2..ac4bfcc33aeb1 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1648,15 +1648,32 @@ struct kvm_s2_fault_desc {
>         unsigned long           hva;
>  };
>
> +struct kvm_s2_fault_vma_info {
> +       unsigned long   mmu_seq;
> +       long            vma_pagesize;
> +       vm_flags_t      vm_flags;
> +       unsigned long   max_map_size;
> +       struct page     *page;
> +       kvm_pfn_t       pfn;
> +       gfn_t           gfn;
> +       bool            mte_allowed;
> +       bool            is_vma_cacheable;
> +       bool            map_writable;
> +};
> +
>  static short kvm_s2_resolve_vma_size(const struct kvm_s2_fault_desc *s2fd,
> -                                    struct vm_area_struct *vma, bool *force_pte)
> +                                    struct kvm_s2_fault_vma_info *s2vi,
> +                                    struct vm_area_struct *vma)
>  {
>         short vma_shift;
>
> -       if (*force_pte)
> +       if (memslot_is_logging(s2fd->memslot)) {
> +               s2vi->max_map_size = PAGE_SIZE;
>                 vma_shift = PAGE_SHIFT;
> -       else
> +       } else {
> +               s2vi->max_map_size = PUD_SIZE;
>                 vma_shift = get_vma_page_shift(vma, s2fd->hva);
> +       }
>
>         switch (vma_shift) {
>  #ifndef __PAGETABLE_PMD_FOLDED
> @@ -1674,7 +1691,7 @@ static short kvm_s2_resolve_vma_size(const struct kvm_s2_fault_desc *s2fd,
>                 fallthrough;
>         case CONT_PTE_SHIFT:
>                 vma_shift = PAGE_SHIFT;
> -               *force_pte = true;
> +               s2vi->max_map_size = PAGE_SIZE;
>                 fallthrough;
>         case PAGE_SHIFT:
>                 break;
> @@ -1685,7 +1702,7 @@ static short kvm_s2_resolve_vma_size(const struct kvm_s2_fault_desc *s2fd,
>         if (s2fd->nested) {
>                 unsigned long max_map_size;
>
> -               max_map_size = *force_pte ? PAGE_SIZE : PUD_SIZE;
> +               max_map_size = min(s2vi->max_map_size, PUD_SIZE);
>
>                 /*
>                  * If we're about to create a shadow stage 2 entry, then we
> @@ -1703,28 +1720,15 @@ static short kvm_s2_resolve_vma_size(const struct kvm_s2_fault_desc *s2fd,
>                 else if (max_map_size >= PAGE_SIZE && max_map_size < PMD_SIZE)
>                         max_map_size = PAGE_SIZE;
>
> -               *force_pte = (max_map_size == PAGE_SIZE);
> +               s2vi->max_map_size = max_map_size;
>                 vma_shift = min_t(short, vma_shift, __ffs(max_map_size));
>         }
>
>         return vma_shift;
>  }
>
> -struct kvm_s2_fault_vma_info {
> -       unsigned long   mmu_seq;
> -       long            vma_pagesize;
> -       vm_flags_t      vm_flags;
> -       struct page     *page;
> -       kvm_pfn_t       pfn;
> -       gfn_t           gfn;
> -       bool            mte_allowed;
> -       bool            is_vma_cacheable;
> -       bool            map_writable;
> -};
> -
>  struct kvm_s2_fault {
>         bool s2_force_noncacheable;
> -       bool force_pte;
>         enum kvm_pgtable_prot prot;
>  };
>
> @@ -1748,7 +1752,7 @@ static int kvm_s2_fault_get_vma_info(const struct kvm_s2_fault_desc *s2fd,
>                 return -EFAULT;
>         }
>
> -       s2vi->vma_pagesize = BIT(kvm_s2_resolve_vma_size(s2fd, vma, &fault->force_pte));
> +       s2vi->vma_pagesize = BIT(kvm_s2_resolve_vma_size(s2fd, s2vi, vma));
>
>         /*
>          * Both the canonical IPA and fault IPA must be aligned to the
> @@ -1933,7 +1937,7 @@ static int kvm_s2_fault_map(const struct kvm_s2_fault_desc *s2fd,
>          * backed by a THP and thus use block mapping if possible.
>          */
>         if (mapping_size == PAGE_SIZE &&
> -           !(fault->force_pte || fault->s2_force_noncacheable)) {
> +           !(s2vi->max_map_size == PAGE_SIZE || fault->s2_force_noncacheable)) {
>                 if (perm_fault_granule > PAGE_SIZE) {
>                         mapping_size = perm_fault_granule;
>                 } else {
> @@ -1990,7 +1994,6 @@ 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 = {
> -               .force_pte = memslot_is_logging(s2fd->memslot),
>                 .prot = KVM_PGTABLE_PROT_R,
>         };
>         void *memcache;
> --
> 2.47.3
>