[PATCH RFC v7 6/7] iommu/arm-smmu-v3: Group aliasing devices into the same IOMMU group

["Peng Fan (OSS)" <peng.fan@oss.nxp.com>]

From: Peng Fan <peng.fan@nxp.com>

Devices sharing a SID must share a single IOMMU domain because the STE
can only point to one CD table at a time. With the domain-owned CD table,
non-PASID devices in that domain share that table directly.

Detect SID aliasing at group-assignment time by looking up the RB tree
for existing owners. Since probe_device() inserts the master before
device_group() is called, skip the device's own stream and look for a
different, already-probed master that shares the same SID.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 33 ++++++++++++++++++++---------
 1 file changed, 23 insertions(+), 10 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index 605d4179caaa9..0ff513f9e0bc1 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -4690,19 +4690,32 @@ static int arm_smmu_set_dirty_tracking(struct iommu_domain *domain,
 
 static struct iommu_group *arm_smmu_device_group(struct device *dev)
 {
-	struct iommu_group *group;
+	struct arm_smmu_master *master = dev_iommu_priv_get(dev);
+	struct arm_smmu_device *smmu = master->smmu;
+	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
+	struct iommu_group *group = NULL;
+	int i;
+
+	mutex_lock(&smmu->streams_mutex);
+	for (i = 0; i < fwspec->num_ids; i++) {
+		struct arm_smmu_stream *stream;
+
+		stream = arm_smmu_find_stream(smmu, fwspec->ids[i]);
+		if (!stream || stream->master == master)
+			continue;
+
+		group = iommu_group_get(stream->master->dev);
+		break;
+	}
+	mutex_unlock(&smmu->streams_mutex);
+
+	if (group)
+		return group;
 
-	/*
-	 * We don't support devices sharing stream IDs other than PCI RID
-	 * aliases, since the necessary ID-to-device lookup becomes rather
-	 * impractical given a potential sparse 32-bit stream ID space.
-	 */
 	if (dev_is_pci(dev))
-		group = pci_device_group(dev);
-	else
-		group = generic_device_group(dev);
+		return pci_device_group(dev);
 
-	return group;
+	return generic_device_group(dev);
 }
 
 static int arm_smmu_of_xlate(struct device *dev,

-- 
2.34.1