Re: [PATCH v2] iommu/vt-d: Fix a bug in intel_iommu_iova_to_phys() for huge page

[Lu Baolu]

Hi,

On 2020/2/21 3:44, Yonghyun Hwang wrote:
> intel_iommu_iova_to_phys() has a bug when it translates an IOVA for a huge
> page onto its corresponding physical address. This commit fixes the bug by
> accomodating the level of page entry for the IOVA and adds IOVA's lower
> address to the physical address.
>
> Signed-off-by: Yonghyun Hwang <yonghyun@xxxxxxxxxx>
> ---
>
> Changes from v1:
> - level cannot be 0. So, the condition, "if (level > 1)", is removed, which results in a simple code.
> - a macro, BIT_MASK, is used to have a bit mask
>
> ---
>   drivers/iommu/intel-iommu.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 932267f49f9a..4fd5c6287b6d 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -5554,7 +5554,9 @@ static phys_addr_t intel_iommu_iova_to_phys(struct iommu_domain *domain,
>   
>   	pte = pfn_to_dma_pte(dmar_domain, iova >> VTD_PAGE_SHIFT, &level);
>   	if (pte)

Need to check whether the pte is present here. Otherwise, the returned
level makes no sense.

Increased change looks like:

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 61c7ef2f33b4..33593fea0250 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -5700,7 +5700,7 @@ static phys_addr_t intel_iommu_iova_to_phys(struct 
iommu_domain *domain,
        u64 phys = 0;

        pte = pfn_to_dma_pte(dmar_domain, iova >> VTD_PAGE_SHIFT, &level);
-       if (pte)
+       if (pte && dma_pte_present(pte))
                phys = dma_pte_addr(pte) +
                        (iova & (BIT_MASK(level_to_offset_bits(level) +
                                                VTD_PAGE_SHIFT) - 1));

> -		phys = dma_pte_addr(pte);
> +		phys = dma_pte_addr(pte) +
> +			(iova & (BIT_MASK(level_to_offset_bits(level) +
> +						VTD_PAGE_SHIFT) - 1));
>   
>   	return phys;
>   }

Best regards,
baolu