Re: [PATCH v7 6/7] KVM: arm64: Ensure FFA ranges are page aligned

[Vincent Donnefort <vdonnefort@google.com>]

On Wed, Jun 17, 2026 at 02:51:29PM +0000, Sebastian Ene wrote:
> From: Mostafa Saleh <smostafa@google.com>
> 
> At the moment we only check that the size of the range is page
> aligned, and truncate the address to the page boundary.
> This make an assumption that TZ will do the same.
> 
> However, it might decide to use the extra offset of the neighbour
> page at the end, which is valid under FFA if NS is using larger
> page size.

I failed to parse this 

But I see 

/* The base IPA of the constituent memory region, aligned to 4 kiB */ 

So it sounds fair to prevent oversharing when PAGE_SIZE > 4KiB

> 
> Harden this check by also checking that the base address is aligned
> and reject it otherwise.
> 
> Fixes: 436090001776 ("KVM: arm64: Handle FFA_MEM_SHARE calls from the host")
> Signed-off-by: Mostafa Saleh <smostafa@google.com>
> Signed-off-by: Sebastian Ene <sebastianene@google.com>

Perhaps the commit description needs some improvement.

The rest looks good.

Reviewed-by: Vincent Donnefort <vdonnefort@google.com>

> ---
>  arch/arm64/kvm/hyp/nvhe/ffa.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
> index 1a2abd0154c6..d7c5701d0584 100644
> --- a/arch/arm64/kvm/hyp/nvhe/ffa.c
> +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
> @@ -352,7 +352,7 @@ static u32 __ffa_host_share_ranges(struct ffa_mem_region_addr_range *ranges,
>  		u64 sz = (u64)range->pg_cnt * FFA_PAGE_SIZE;
>  		u64 pfn = hyp_phys_to_pfn(range->address);
>  
> -		if (!PAGE_ALIGNED(sz))
> +		if (!PAGE_ALIGNED(sz | range->address))
>  			break;
>  
>  		if (__pkvm_host_share_ffa(pfn, sz / PAGE_SIZE))
> @@ -372,7 +372,7 @@ static u32 __ffa_host_unshare_ranges(struct ffa_mem_region_addr_range *ranges,
>  		u64 sz = (u64)range->pg_cnt * FFA_PAGE_SIZE;
>  		u64 pfn = hyp_phys_to_pfn(range->address);
>  
> -		if (!PAGE_ALIGNED(sz))
> +		if (!PAGE_ALIGNED(sz | range->address))
>  			break;
>  
>  		if (__pkvm_host_unshare_ffa(pfn, sz / PAGE_SIZE))
> -- 
> 2.54.0.1136.gdb2ca164c4-goog
>