[PATCH] iommu/dma-iommu: respect established iova region limits

[Nate Watterson <nwatters-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>]

In the current dma-iommu implementation, the upper limit used when
allocating iovas is based on the calling device's dma_mask without
considering the potentially more restrictive iova limits established
in iommu_dma_init_domain. To ensure that iovas are allocated within
the expected iova region, this patch adds logic in __alloc_iova to
clip input dma_limit values that are out of bounds.

Signed-off-by: Nate Watterson <nwatters-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
---
 drivers/iommu/dma-iommu.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index ea5a9eb..2066066 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -157,11 +157,14 @@ static struct iova *__alloc_iova(struct iova_domain *iovad, size_t size,
 	unsigned long shift = iova_shift(iovad);
 	unsigned long length = iova_align(iovad, size) >> shift;
 
+	/* Respect the upper limit established in iommu_dma_init_domain */
+	dma_limit = min_t(dma_addr_t, dma_limit >> shift, iovad->dma_32bit_pfn);
+
 	/*
 	 * Enforce size-alignment to be safe - there could perhaps be an
 	 * attribute to control this per-device, or at least per-domain...
 	 */
-	return alloc_iova(iovad, length, dma_limit >> shift, true);
+	return alloc_iova(iovad, length, dma_limit, true);
 }
 
 /* The IOVA allocator knows what we mapped, so just unmap whatever that was */
-- 
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