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Subject[PATCH] iommu/vt-d: Return the correct dma mask when we are bypassing the IOMMU
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>
---
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
--
2.21.0
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