[PATCH v2 2/5] intel-iommu: Obey coherent_dma_mask for alloc_coherent on passthrough

[Alex Williamson <alex.williamson@hp.com>]

intel_alloc_coherent() needs to follow DMA mapping convention and
make use of the coherent_dma_mask of the device for identity mappings.
Without this, devices may get buffers they can't use.

Signed-off-by: Alex Williamson <alex.williamson@hp.com>
---

 v2: Abandon attempt to create a common dma_generic_alloc_coherent,
     patch 1/5 is now defunct.  Patches 3-5 are unchanged.

 drivers/pci/intel-iommu.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
index b1e97e6..272261e 100644
--- a/drivers/pci/intel-iommu.c
+++ b/drivers/pci/intel-iommu.c
@@ -2582,7 +2582,7 @@ static dma_addr_t __intel_map_single(struct device *hwdev, phys_addr_t paddr,
 	BUG_ON(dir == DMA_NONE);
 
 	if (iommu_no_mapping(hwdev))
-		return paddr;
+		return paddr + size > dma_mask ? 0 : paddr;
 
 	domain = get_valid_domain_for_dev(pdev);
 	if (!domain)
@@ -2767,7 +2767,11 @@ static void *intel_alloc_coherent(struct device *hwdev, size_t size,
 
 	size = PAGE_ALIGN(size);
 	order = get_order(size);
-	flags &= ~(GFP_DMA | GFP_DMA32);
+
+	if (!iommu_no_mapping(hwdev))
+		flags &= ~(GFP_DMA | GFP_DMA32);
+	else if (hwdev->coherent_dma_mask != DMA_BIT_MASK(64))
+		flags |= GFP_DMA;
 
 	vaddr = (void *)__get_free_pages(flags, order);
 	if (!vaddr)