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SubjectRe: [PATCH] iommu/vt-d: Return the correct dma mask when we are bypassing the IOMMU
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Hi,

On 10/8/19 10:33 PM, Arvind Sankar wrote:
> We must return a mask covering the full physical RAM when bypassing the
> IOMMU mapping. Also, in iommu_need_mapping, we need to check using
> dma_direct_get_required_mask to ensure that the device's dma_mask can
> cover physical RAM before deciding to bypass IOMMU mapping.
>
> Fixes: 249baa547901 ("dma-mapping: provide a better default ->get_required_mask")
> Reported-by: Arvind Sankar <nivedita@alum.mit.edu>
> Tested-by: Arvind Sankar <nivedita@alum.mit.edu>
> Originally-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> Fixed-by: Arvind Sankar <nivedita@alum.mit.edu>
> Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>

This patch looks good to me.

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>

> ---
> drivers/iommu/intel-iommu.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 3f974919d3bd..79e35b3180ac 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -3471,7 +3471,7 @@ static bool iommu_need_mapping(struct device *dev)
> if (dev->coherent_dma_mask && dev->coherent_dma_mask < dma_mask)
> dma_mask = dev->coherent_dma_mask;
>
> - if (dma_mask >= dma_get_required_mask(dev))
> + if (dma_mask >= dma_direct_get_required_mask(dev))
> return false;
>
> /*
> @@ -3775,6 +3775,13 @@ static int intel_map_sg(struct device *dev, struct scatterlist *sglist, int nele
> return nelems;
> }
>
> +static u64 intel_get_required_mask(struct device *dev)
> +{
> + if (!iommu_need_mapping(dev))
> + return dma_direct_get_required_mask(dev);
> + return DMA_BIT_MASK(32);
> +}
> +
> static const struct dma_map_ops intel_dma_ops = {
> .alloc = intel_alloc_coherent,
> .free = intel_free_coherent,
> @@ -3787,6 +3794,7 @@ static const struct dma_map_ops intel_dma_ops = {
> .dma_supported = dma_direct_supported,
> .mmap = dma_common_mmap,
> .get_sgtable = dma_common_get_sgtable,
> + .get_required_mask = intel_get_required_mask,
> };
>
> static void
>

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