[PATCH kernel v4 2/2] KVM: PPC: Check if IOMMU page is contained in the pinned physical page

[Michael Ellerman]

Alexey Kardashevskiy <aik at ozlabs.ru> writes:

> diff --git a/arch/powerpc/mm/mmu_context_iommu.c b/arch/powerpc/mm/mmu_context_iommu.c
> index abb4364..11e1029 100644
> --- a/arch/powerpc/mm/mmu_context_iommu.c
> +++ b/arch/powerpc/mm/mmu_context_iommu.c
> @@ -159,6 +161,7 @@ long mm_iommu_get(struct mm_struct *mm, unsigned long ua, unsigned long entries,
>  		goto unlock_exit;
>  	}
>  
> +	mem->pageshift = __builtin_ctzl(ua | (entries << PAGE_SHIFT));

__builtin_ctzl(0) is undefined, so are we guaranteed that
(ua | (entries << PAGE_SHIFT)) is never zero? I couldn't convince
myself.

> @@ -199,9 +202,17 @@ long mm_iommu_get(struct mm_struct *mm, unsigned long ua, unsigned long entries,
>  			}
>  		}
>  populate:
> +		pageshift = PAGE_SHIFT;
> +		if (PageCompound(page))
> +			pageshift += compound_order(compound_head(page));
> +		mem->pageshift = min(mem->pageshift, pageshift);
>  		mem->hpas[i] = page_to_pfn(page) << PAGE_SHIFT;
>  	}
>  
> +	/* We have an incomplete huge page, default to PAGE_SHIFT */
> +	if (head)
> +		mem->pageshift = PAGE_SHIFT;
> +

You never set head AFIACS? (other than in the initialiser)

cheers