[PATCH] iommu: amd/intel: Remove multifunction assumption around grouping

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

If a device is multifunction and does not have ACS enabled then we
assume that the entire package lacks ACS and use function 0 as the
base of the group.  The PCIe spec however states that components are
permitted to implement ACS on some, none, or all of their applicable
functions.  It's therefore conceivable that function 0 may be fully
independent and support ACS while other functions do not.  Instead
use the lowest function of the slot that does not have ACS enabled
as the base of the group.  This may be the current device, which is
intentional.  So long as we use a consistent algorithm, all the
non-ACS functions will be grouped together and ACS functions will
get separate groups.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 drivers/iommu/amd_iommu.c   |   25 +++++++++++++++++++------
 drivers/iommu/intel-iommu.c |   25 +++++++++++++++++++------
 2 files changed, 38 insertions(+), 12 deletions(-)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 1d84be1..565c745 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -287,14 +287,27 @@ static struct pci_dev *get_isolation_root(struct pci_dev *pdev)
 
 	/*
 	 * If it's a multifunction device that does not support our
-	 * required ACS flags, add to the same group as function 0.
+	 * required ACS flags, add to the same group as lowest numbered
+	 * function that also does not suport the required ACS flags.
 	 */
 	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)));
+	    !pci_acs_enabled(dma_pdev, REQ_ACS_FLAGS)) {
+		u8 i, slot = PCI_SLOT(dma_pdev->devfn);
+
+		for (i = 0; i < 8; i++) {
+			struct pci_dev *tmp;
+
+			tmp = pci_get_slot(dma_pdev->bus, PCI_DEVFN(slot, i));
+			if (!tmp)
+				continue;
+
+			if (!pci_acs_enabled(tmp, REQ_ACS_FLAGS)) {
+				swap_pci_ref(&dma_pdev, tmp);
+				break;
+			}
+			pci_dev_put(tmp);
+		}
+	}
 
 	/*
 	 * Devices on the root bus go through the iommu.  If that's not us,
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index b4f0e28..eec0d3e 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -4182,14 +4182,27 @@ static int intel_iommu_add_device(struct device *dev)
 
 	/*
 	 * If it's a multifunction device that does not support our
-	 * required ACS flags, add to the same group as function 0.
+	 * required ACS flags, add to the same group as lowest numbered
+	 * function that also does not suport the required ACS flags.
 	 */
 	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)));
+	    !pci_acs_enabled(dma_pdev, REQ_ACS_FLAGS)) {
+		u8 i, slot = PCI_SLOT(dma_pdev->devfn);
+
+		for (i = 0; i < 8; i++) {
+			struct pci_dev *tmp;
+
+			tmp = pci_get_slot(dma_pdev->bus, PCI_DEVFN(slot, i));
+			if (!tmp)
+				continue;
+
+			if (!pci_acs_enabled(tmp, REQ_ACS_FLAGS)) {
+				swap_pci_ref(&dma_pdev, tmp);
+				break;
+			}
+			pci_dev_put(tmp);
+		}
+	}
 
 	/*
 	 * Devices on the root bus go through the iommu.  If that's not us,