linux-kernel - Re: [PATCH v2] iommu/vt-d: Fix a bug in intel_iommu_iova_to

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Message-ID: <20200220195020.GA1193@epycbox.lan>
Date:   Thu, 20 Feb 2020 11:50:20 -0800
From:   Moritz Fischer <mdf@...nel.org>
To:     Yonghyun Hwang <yonghyun@...gle.com>
Cc:     David Woodhouse <dwmw2@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Havard Skinnemoen <hskinnemoen@...gle.com>,
        Deepa Dinamani <deepadinamani@...gle.com>,
        Moritz Fischer <mdf@...nel.org>
Subject: Re: [PATCH v2] iommu/vt-d: Fix a bug in intel_iommu_iova_to_phys()
 for huge page

Hi Yonghyun,

On Thu, Feb 20, 2020 at 11:44:31AM -0800, 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.
> 
D'oh I meant to add a Cc: stable@...r.kernel.org here ... :)
> Signed-off-by: Yonghyun Hwang <yonghyun@...gle.com>
> ---
> 
> 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)
> -		phys = dma_pte_addr(pte);
> +		phys = dma_pte_addr(pte) +
> +			(iova & (BIT_MASK(level_to_offset_bits(level) +
> +						VTD_PAGE_SHIFT) - 1));
>  
>  	return phys;
>  }
> -- 
> 2.25.0.265.gbab2e86ba0-goog
> 

Cheers,
Moritz