linux-kernel - [PATCH v2 6/7] intel-iommu: Make use of DMA quirks and ACS checks in IOMMU groups

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Date:	Wed, 30 May 2012 14:19:43 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	joerg.roedel@....com, dwmw2@...radead.org,
	iommu@...ts.linux-foundation.org
Cc:	bhelgaas@...gle.com, benh@...nel.crashing.org, aik@...abs.ru,
	david@...son.dropbear.id.au, konrad.wilk@...cle.com,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	gregkh@...uxfoundation.org, ddutile@...hat.com,
	alex.williamson@...hat.com, liuj97@...il.com
Subject: [PATCH v2 6/7] intel-iommu: Make use of DMA quirks and ACS checks in
 IOMMU groups

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

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

 drivers/iommu/intel-iommu.c |   25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 4a43452..ebf2b31 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -4090,6 +4090,14 @@ static int intel_iommu_domain_has_cap(struct iommu_domain *domain,
 	return 0;
 }
 
+static void swap_pci_ref(struct pci_dev **from, struct pci_dev *to)
+{
+	pci_dev_put(*from);
+	*from = to;
+}
+
+#define REQ_ACS_FLAGS	(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);
@@ -4112,6 +4120,23 @@ static int intel_iommu_add_device(struct device *dev)
 	} else
 		dma_pdev = pci_dev_get(pdev);
 
+	swap_pci_ref(&dma_pdev, pci_get_dma_source(dma_pdev));
+
+	if (dma_pdev->multifunction &&
+	    !pci_acs_enabled(dma_pdev, REQ_ACS_FLAGS))
+		swap_pci_ref(&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, REQ_ACS_FLAGS))
+			break;
+
+		swap_pci_ref(&dma_pdev, pci_dev_get(dma_pdev->bus->self));
+	}
+
 	group = iommu_group_get(&dma_pdev->dev);
 	pci_dev_put(dma_pdev);
 	if (!group) {

--
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