iommu/arm-smmu: Don't inadvertently reject multiple SMMUv3s

We now delay installing our per-bus iommu_ops until we know an SMMU has
successfully probed, as they don't serve much purpose beforehand, and
doing so also avoids fights between multiple IOMMU drivers in a single
kernel. However, the upshot of passing the return value of bus_set_iommu()
back from our probe function is that if there happens to be more than
one SMMUv3 device in a system, the second and subsequent probes will
wind up returning -EBUSY to the driver core and getting torn down again.

Avoid re-setting ops if ours are already installed, so that any genuine
failures stand out.

Fixes: 08d4ca2a672b ("iommu/arm-smmu: Support non-PCI devices with SMMUv3")
CC: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
CC: Hanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 15c01c3..e6f9b2d 100644 (file)
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -2636,17 +2636,26 @@ static int arm_smmu_device_dt_probe(struct platform_device *pdev)
        /* And we're up. Go go go! */
        of_iommu_set_ops(dev->of_node, &arm_smmu_ops);
 #ifdef CONFIG_PCI
-       pci_request_acs();
-       ret = bus_set_iommu(&pci_bus_type, &arm_smmu_ops);
-       if (ret)
-               return ret;
+       if (pci_bus_type.iommu_ops != &arm_smmu_ops) {
+               pci_request_acs();
+               ret = bus_set_iommu(&pci_bus_type, &arm_smmu_ops);
+               if (ret)
+                       return ret;
+       }
 #endif
 #ifdef CONFIG_ARM_AMBA
-       ret = bus_set_iommu(&amba_bustype, &arm_smmu_ops);
-       if (ret)
-               return ret;
+       if (amba_bustype.iommu_ops != &arm_smmu_ops) {
+               ret = bus_set_iommu(&amba_bustype, &arm_smmu_ops);
+               if (ret)
+                       return ret;
+       }
 #endif
-       return bus_set_iommu(&platform_bus_type, &arm_smmu_ops);
+       if (platform_bus_type.iommu_ops != &arm_smmu_ops) {
+               ret = bus_set_iommu(&platform_bus_type, &arm_smmu_ops);
+               if (ret)
+                       return ret;
+       }
+       return 0;
 }
 
 static int arm_smmu_device_remove(struct platform_device *pdev)