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 Signed-off-by: Mike Travis Reviewed-by: Mike Habeck --- 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; } --