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From:   Sasha Levin <Alexander.Levin@microsoft.com>
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        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     Robin Murphy <robin.murphy@arm.com>,
        Christoph Hellwig <hch@lst.de>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL 4.14 66/89] iommu/dma: Respect bus DMA limit for IOVAs
Thread-Topic: [PATCH AUTOSEL 4.14 66/89] iommu/dma: Respect bus DMA limit for
 IOVAs
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Date:   Sun, 2 Sep 2018 13:07:30 +0000
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From: Robin Murphy <robin.murphy@arm.com>

[ Upstream commit 03bfdc31176cbe21e456f889ccbbf67568831149 ]

Take the new bus limit into account (when present) for IOVA allocations,
to accommodate those SoCs which integrate off-the-shelf IP blocks with
narrower interconnects such that the link between a device output and an
IOMMU input can truncate DMA addresses to even fewer bits than the
native size of either block's interface would imply.

Eventually it might make sense for the DMA core to apply this constraint
up-front in dma_set_mask() and friends, but for now this seems like the
least risky approach.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 drivers/iommu/dma-iommu.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 9d1cebe7f6cb..de8743a7fb78 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -381,6 +381,9 @@ static dma_addr_t iommu_dma_alloc_iova(struct iommu_dom=
ain *domain,
 	if (iova_len < (1 << (IOVA_RANGE_CACHE_MAX_SIZE - 1)))
 		iova_len =3D roundup_pow_of_two(iova_len);
=20
+	if (dev->bus_dma_mask)
+		dma_limit &=3D dev->bus_dma_mask;
+
 	if (domain->geometry.force_aperture)
 		dma_limit =3D min(dma_limit, domain->geometry.aperture_end);
=20
--=20
2.17.1