[PATCH v2] iommu/arm-smmu: Don't inadvertently reject multiple SMMUv3s

[Robin Murphy]

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 <***@arm.com>
CC: Hanjun Guo <***@linaro.org>
Signed-off-by: Robin Murphy <***@arm.com>
---
drivers/iommu/arm-smmu-v3.c | 25 +++++++++++++++++--------
1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 15c01c3cd540..e6f9b2d745ca 100644
--- 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)

[Joerg Roedel]

Post by Robin Murphy
drivers/iommu/arm-smmu-v3.c | 25 +++++++++++++++++--------
1 file changed, 17 insertions(+), 8 deletions(-)

This looks better, thanks. Cherry-picked the other fix from the
pull-request and applied this on-top.


Joerg