[PATCH 2/2] iommu/arm-smmu-v3: Report stalled S2 events

[Mostafa Saleh <smostafa@google.com>]

Previously, S2 stall was disabled and in case there was an event it
wouldn't be reported on the assumption that it's always pinned  by VFIO.

However, now since we can enable stall, devices that use S2 outside
VFIO should be able to report the stalls similar to S1.

Also, to keep the old behaviour were S2 events from nested domains were
not reported as they are pinned (from VFIO) add a new flag to track this.

Signed-off-by: Mostafa Saleh <smostafa@google.com>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 18 +++++++++++++-----
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h |  2 ++
 2 files changed, 15 insertions(+), 5 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 8d573d9ca93c..ffa865529d73 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -1733,6 +1733,7 @@ static int arm_smmu_handle_evt(struct arm_smmu_device *smmu, u64 *evt)
 	u32 sid = FIELD_GET(EVTQ_0_SID, evt[0]);
 	struct iopf_fault fault_evt = { };
 	struct iommu_fault *flt = &fault_evt.fault;
+	struct arm_smmu_domain *smmu_domain;
 
 	switch (FIELD_GET(EVTQ_0_ID, evt[0])) {
 	case EVT_ID_TRANSLATION_FAULT:
@@ -1744,10 +1745,6 @@ static int arm_smmu_handle_evt(struct arm_smmu_device *smmu, u64 *evt)
 		return -EOPNOTSUPP;
 	}
 
-	/* Stage-2 is always pinned at the moment */
-	if (evt[1] & EVTQ_1_S2)
-		return -EFAULT;
-
 	if (!(evt[1] & EVTQ_1_STALL))
 		return -EOPNOTSUPP;
 
@@ -1782,6 +1779,15 @@ static int arm_smmu_handle_evt(struct arm_smmu_device *smmu, u64 *evt)
 		goto out_unlock;
 	}
 
+	/* It is guaranteed that smmu_domain exists as EVTQ_1_STALL is checked. */
+	smmu_domain = to_smmu_domain(iommu_get_domain_for_dev(master->dev));
+
+	/* nesting domain is always pinned at the moment */
+	if (smmu_domain->enable_nesting) {
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
 	iommu_report_device_fault(master->dev, &fault_evt);
 out_unlock:
 	mutex_unlock(&smmu->streams_mutex);
@@ -3373,8 +3379,10 @@ static int arm_smmu_enable_nesting(struct iommu_domain *domain)
 	mutex_lock(&smmu_domain->init_mutex);
 	if (smmu_domain->smmu)
 		ret = -EPERM;
-	else
+	else {
 		smmu_domain->stage = ARM_SMMU_DOMAIN_S2;
+		smmu_domain->enable_nesting = true;
+	}
 	mutex_unlock(&smmu_domain->init_mutex);
 
 	return ret;
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
index 0dc7ad43c64c..f66efeec2cf8 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -745,6 +745,8 @@ struct arm_smmu_domain {
 	spinlock_t			devices_lock;
 
 	struct mmu_notifier		mmu_notifier;
+
+	bool				enable_nesting;
 };
 
 /* The following are exposed for testing purposes. */
-- 
2.46.0.76.ge559c4bf1a-goog