[PATCH 6/7] intel-iommu: Make use of DMA quirks and ACS checks in IOMMU groups

[Alex Williamson <alex.williamson-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

Work around broken devices and adhere to ACS support when determining
IOMMU grouping.

Signed-off-by: Alex Williamson <alex.williamson-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---

 drivers/iommu/intel-iommu.c |   18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index d42ce10..c26d21b 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -4090,6 +4090,8 @@ static int intel_iommu_domain_has_cap(struct iommu_domain *domain,
 	return 0;
 }
 
+#define PCI_ACS_ENABLED	(PCI_ACS_SV | PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_UF)
+
 static int intel_iommu_add_device(struct device *dev)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
@@ -4116,6 +4118,22 @@ static int intel_iommu_add_device(struct device *dev)
 		dma_pdev = pci_get_slot(pdev->bus,
 					PCI_DEVFN(PCI_SLOT(pdev->devfn), 0));
 
+	dma_pdev = pci_dma_source(dma_pdev);
+
+	if (dma_pdev->multifunction &&
+	    !pci_acs_enabled(dma_pdev, PCI_ACS_ENABLED))
+		dma_pdev = pci_get_slot(dma_pdev->bus,
+					PCI_DEVFN(PCI_SLOT(dma_pdev->devfn),
+					0));
+
+	while (!pci_is_root_bus(dma_pdev->bus)) {
+		if (pci_acs_path_enabled(dma_pdev->bus->self,
+					 NULL, PCI_ACS_ENABLED))
+			break;
+
+		dma_pdev = dma_pdev->bus->self;
+	}
+
 	group = iommu_group_get(&dma_pdev->dev);
 	if (!group) {
 		group = iommu_group_alloc();