Re: [PATCH] KVM: arm64: Use consistent type for pool size

[Fuad Tabba]

On Wed, 15 Jul 2026 at 16:01, Mostafa Saleh <smostafa@xxxxxxxxxx> wrote:
>
> All the pool sizes in the hypervisor are "unsigned long" but when
> they get passed to hyp_early_alloc_contig() or hyp_pool_init() they get
> truncated to 32-bits.
>
> That is not a big problem at the moment as to overflow this we need
> 4G bytes of carveout (2 TB of host or guest system memory).
>
> However when new users are added (as IOMMU) it is hard to reason
> about the carveout size anymore.
>
> Signed-off-by: Mostafa Saleh <smostafa@xxxxxxxxxx>

Reviewed-by: Fuad Tabba <fuad.tabba@xxxxxxxxx>

Cheers,
/fuad


> ---
> For example in the SMMUv3 to avoid this overflow, I add a cap
> for the pools size to UINT_MAX to work around this:
> https://lore.kernel.org/linux-iommu/20260715115906.2664882-9-smostafa@xxxxxxxxxx/
> ---
>  arch/arm64/kvm/hyp/include/nvhe/early_alloc.h | 2 +-
>  arch/arm64/kvm/hyp/include/nvhe/gfp.h         | 4 ++--
>  arch/arm64/kvm/hyp/nvhe/early_alloc.c         | 2 +-
>  arch/arm64/kvm/hyp/nvhe/page_alloc.c          | 6 +++---
>  4 files changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm64/kvm/hyp/include/nvhe/early_alloc.h b/arch/arm64/kvm/hyp/include/nvhe/early_alloc.h
> index dc61aaa56f31..462883c4e325 100644
> --- a/arch/arm64/kvm/hyp/include/nvhe/early_alloc.h
> +++ b/arch/arm64/kvm/hyp/include/nvhe/early_alloc.h
> @@ -7,7 +7,7 @@
>  void hyp_early_alloc_init(void *virt, unsigned long size);
>  unsigned long hyp_early_alloc_nr_used_pages(void);
>  void *hyp_early_alloc_page(void *arg);
> -void *hyp_early_alloc_contig(unsigned int nr_pages);
> +void *hyp_early_alloc_contig(unsigned long nr_pages);
>
>  extern struct kvm_pgtable_mm_ops hyp_early_alloc_mm_ops;
>
> diff --git a/arch/arm64/kvm/hyp/include/nvhe/gfp.h b/arch/arm64/kvm/hyp/include/nvhe/gfp.h
> index 3766333bace9..3a428dc40b14 100644
> --- a/arch/arm64/kvm/hyp/include/nvhe/gfp.h
> +++ b/arch/arm64/kvm/hyp/include/nvhe/gfp.h
> @@ -29,6 +29,6 @@ void hyp_get_page(struct hyp_pool *pool, void *addr);
>  void hyp_put_page(struct hyp_pool *pool, void *addr);
>
>  /* Used pages cannot be freed */
> -int hyp_pool_init(struct hyp_pool *pool, u64 pfn, unsigned int nr_pages,
> -                 unsigned int reserved_pages);
> +int hyp_pool_init(struct hyp_pool *pool, u64 pfn, unsigned long nr_pages,
> +                 unsigned long reserved_pages);
>  #endif /* __KVM_HYP_GFP_H */
> diff --git a/arch/arm64/kvm/hyp/nvhe/early_alloc.c b/arch/arm64/kvm/hyp/nvhe/early_alloc.c
> index 00de04153cc6..9fef0c7d2185 100644
> --- a/arch/arm64/kvm/hyp/nvhe/early_alloc.c
> +++ b/arch/arm64/kvm/hyp/nvhe/early_alloc.c
> @@ -21,7 +21,7 @@ unsigned long hyp_early_alloc_nr_used_pages(void)
>         return (cur - base) >> PAGE_SHIFT;
>  }
>
> -void *hyp_early_alloc_contig(unsigned int nr_pages)
> +void *hyp_early_alloc_contig(unsigned long nr_pages)
>  {
>         unsigned long size = (nr_pages << PAGE_SHIFT);
>         void *ret = (void *)cur;
> diff --git a/arch/arm64/kvm/hyp/nvhe/page_alloc.c b/arch/arm64/kvm/hyp/nvhe/page_alloc.c
> index 57f86aa0f82f..51460d420c94 100644
> --- a/arch/arm64/kvm/hyp/nvhe/page_alloc.c
> +++ b/arch/arm64/kvm/hyp/nvhe/page_alloc.c
> @@ -229,12 +229,12 @@ void *hyp_alloc_pages(struct hyp_pool *pool, u8 order)
>         return hyp_page_to_virt(p);
>  }
>
> -int hyp_pool_init(struct hyp_pool *pool, u64 pfn, unsigned int nr_pages,
> -                 unsigned int reserved_pages)
> +int hyp_pool_init(struct hyp_pool *pool, u64 pfn, unsigned long nr_pages,
> +                 unsigned long reserved_pages)
>  {
>         phys_addr_t phys = hyp_pfn_to_phys(pfn);
>         struct hyp_page *p;
> -       int i;
> +       unsigned long i;
>
>         hyp_spin_lock_init(&pool->lock);
>         pool->max_order = min(MAX_PAGE_ORDER,
> --
> 2.55.0.141.g00534a21ce-goog
>