iommu/arm-smmu-v3: Add stall support for platform devices

The SMMU provides a Stall model for handling page faults in platform
devices. It is similar to PCIe PRI, but doesn't require devices to have
their own translation cache. Instead, faulting transactions are parked
and the OS is given a chance to fix the page tables and retry the
transaction.

Enable stall for devices that support it (opt-in by firmware). When an
event corresponds to a translation error, call the IOMMU fault handler.
If the fault is recoverable, it will call us back to terminate or
continue the stall.

To use stall device drivers need to enable IOMMU_DEV_FEAT_IOPF, which
initializes the fault queue for the device.

Tested-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Link: https://lore.kernel.org/r/20210526161927.24268-4-jean-philippe@linaro.org
Signed-off-by: Will Deacon <will@kernel.org>

drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c

@@ -435,18 +435,22 @@ bool arm_smmu_sva_supported(struct arm_smmu_device *smmu)
 	return true;
 }
 
-static bool arm_smmu_iopf_supported(struct arm_smmu_master *master)
+bool arm_smmu_master_iopf_supported(struct arm_smmu_master *master)
 {
-	return false;
+	/* We're not keeping track of SIDs in fault events */
+	if (master->num_streams != 1)
+		return false;
+
+	return master->stall_enabled;
 }
 
 bool arm_smmu_master_sva_supported(struct arm_smmu_master *master)
 {
 	if (!(master->smmu->features & ARM_SMMU_FEAT_SVA))
 		return false;
 
-	/* SSID and IOPF support are mandatory for the moment */
-	return master->ssid_bits && arm_smmu_iopf_supported(master);
+	/* SSID support is mandatory for the moment */
+	return master->ssid_bits;
 }
 
 bool arm_smmu_master_sva_enabled(struct arm_smmu_master *master)
@@ -459,13 +463,55 @@ bool arm_smmu_master_sva_enabled(struct arm_smmu_master *master)
 	return enabled;
 }
 
+static int arm_smmu_master_sva_enable_iopf(struct arm_smmu_master *master)
+{
+	int ret;
+	struct device *dev = master->dev;
+
+	/*
+	 * Drivers for devices supporting PRI or stall should enable IOPF first.
+	 * Others have device-specific fault handlers and don't need IOPF.
+	 */
+	if (!arm_smmu_master_iopf_supported(master))
+		return 0;
+
+	if (!master->iopf_enabled)
+		return -EINVAL;
+
+	ret = iopf_queue_add_device(master->smmu->evtq.iopf, dev);
+	if (ret)
+		return ret;
+
+	ret = iommu_register_device_fault_handler(dev, iommu_queue_iopf, dev);
+	if (ret) {
+		iopf_queue_remove_device(master->smmu->evtq.iopf, dev);
+		return ret;
+	}
+	return 0;
+}
+
+static void arm_smmu_master_sva_disable_iopf(struct arm_smmu_master *master)
+{
+	struct device *dev = master->dev;
+
+	if (!master->iopf_enabled)
+		return;
+
+	iommu_unregister_device_fault_handler(dev);
+	iopf_queue_remove_device(master->smmu->evtq.iopf, dev);
+}
+
 int arm_smmu_master_enable_sva(struct arm_smmu_master *master)
 {
+	int ret;
+
 	mutex_lock(&sva_lock);
-	master->sva_enabled = true;
+	ret = arm_smmu_master_sva_enable_iopf(master);
+	if (!ret)
+		master->sva_enabled = true;
 	mutex_unlock(&sva_lock);
 
-	return 0;
+	return ret;
 }
 
 int arm_smmu_master_disable_sva(struct arm_smmu_master *master)
@@ -476,6 +522,7 @@ int arm_smmu_master_disable_sva(struct arm_smmu_master *master)
 		mutex_unlock(&sva_lock);
 		return -EBUSY;
 	}
+	arm_smmu_master_sva_disable_iopf(master);
 	master->sva_enabled = false;
 	mutex_unlock(&sva_lock);