[PATCH 1/7] Intel pci: Check for identity mapping candidate using system dma mask

[Mike Travis]

	The identity mapping code appears to make the assumption that
	if the devices dma_mask is greater than 32bits the device can
	use identity mapping.  But that is not true, take the case 
	where we have a 40bit device in a 44bit architecture.  The
	device can potentially receive a physical address that it
	will truncate and cause incorrect addresses to be used.

	Instead check to see if the device's dma_mask is large enough
	to address the system's dma_mask.

From: Chris Wright <chrisw@xxxxxxxxxxxx>
Signed-off-by: Mike Travis <travis@xxxxxxx>
Reviewed-by: Mike Habeck <habeck@xxxxxxx>
---
 drivers/pci/intel-iommu.c |   15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

--- linux.orig/drivers/pci/intel-iommu.c
+++ linux/drivers/pci/intel-iommu.c
@@ -2187,8 +2187,19 @@ static int iommu_should_identity_map(str
 	 * Assume that they will -- if they turn out not to be, then we can 
 	 * take them out of the 1:1 domain later.
 	 */
-	if (!startup)
-		return pdev->dma_mask > DMA_BIT_MASK(32);
+	if (!startup) {
+		/*
+		 * If the device's dma_mask is less than the system's memory
+		 * size then this is not a candidate for identity mapping.
+		 */
+		u64 dma_mask = pdev->dma_mask;
+
+		if (pdev->dev.coherent_dma_mask &&
+		    pdev->dev.coherent_dma_mask < dma_mask)
+			dma_mask = pdev->dev.coherent_dma_mask;
+
+		return dma_mask >= dma_get_required_mask(&pdev->dev);
+	}
 
 	return 1;
 }

-- 
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