[PATCH v5 02/15] iommu/arm-smmu-v3: Add arm_smmu_attach_release()

[Nicolin Chen <nicolinc@nvidia.com>]

The IOPF teardown is done in arm_smmu_remove_master_domain() when releasing
the master_domain on detach, under the global arm_smmu_asid_lock mutex.

A later change will add an IOPF workqueue flush to that teardown, which can
block on a user-faulting page-fault handler. Holding the arm_smmu_asid_lock
across it would stall every unrelated attachment in the system.

Split the teardown out of arm_smmu_remove_master_domain(), to a new helper
arm_smmu_attach_release() that runs after arm_smmu_asid_lock is released.

No functional change: the old master_domain belongs to no other device, so
freeing it outside the lock stays safe, still under iommu_group->mutex.

Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h   |  2 +
 .../arm/arm-smmu-v3/arm-smmu-v3-iommufd.c     |  1 +
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c   | 44 ++++++++++++++-----
 3 files changed, 36 insertions(+), 11 deletions(-)

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 50f8321e979ce..5b89bad71c102 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -1204,12 +1204,14 @@ struct arm_smmu_attach_state {
 	struct arm_smmu_vmaster *vmaster;
 	struct arm_smmu_inv_state old_domain_invst;
 	struct arm_smmu_inv_state new_domain_invst;
+	struct arm_smmu_master_domain *old_master_domain;
 	bool ats_enabled;
 };
 
 int arm_smmu_attach_prepare(struct arm_smmu_attach_state *state,
 			    struct iommu_domain *new_domain);
 void arm_smmu_attach_commit(struct arm_smmu_attach_state *state);
+void arm_smmu_attach_release(struct arm_smmu_attach_state *state);
 void arm_smmu_install_ste_for_dev(struct arm_smmu_master *master,
 				  const struct arm_smmu_ste *target);
 
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
index 25982bdbcbd9a..fce026efa44f1 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
@@ -194,6 +194,7 @@ static int arm_smmu_attach_dev_nested(struct iommu_domain *domain,
 	arm_smmu_install_ste_for_dev(master, &ste);
 	arm_smmu_attach_commit(&state);
 	mutex_unlock(&arm_smmu_asid_lock);
+	arm_smmu_attach_release(&state);
 	return 0;
 }
 
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 81baafaffc410..759d0e1126b30 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -3285,9 +3285,9 @@ arm_smmu_master_build_invs(struct arm_smmu_master *master, bool ats_enabled,
 	return master->build_invs;
 }
 
-static void arm_smmu_remove_master_domain(struct arm_smmu_master *master,
-					  struct iommu_domain *domain,
-					  ioasid_t ssid)
+static struct arm_smmu_master_domain *
+arm_smmu_remove_master_domain(struct arm_smmu_master *master,
+			      struct iommu_domain *domain, ioasid_t ssid)
 {
 	struct arm_smmu_domain *smmu_domain = to_smmu_domain_devices(domain);
 	struct arm_smmu_master_domain *master_domain;
@@ -3295,7 +3295,7 @@ static void arm_smmu_remove_master_domain(struct arm_smmu_master *master,
 	unsigned long flags;
 
 	if (!smmu_domain)
-		return;
+		return NULL;
 
 	if (domain->type == IOMMU_DOMAIN_NESTED)
 		nested_ats_flush = to_smmu_nested_domain(domain)->enable_ats;
@@ -3310,8 +3310,24 @@ static void arm_smmu_remove_master_domain(struct arm_smmu_master *master,
 	}
 	spin_unlock_irqrestore(&smmu_domain->devices_lock, flags);
 
+	/* arm_smmu_attach_release() will free it */
+	return master_domain;
+}
+
+/* Release the old master_domain detached by arm_smmu_remove_master_domain() */
+void arm_smmu_attach_release(struct arm_smmu_attach_state *state)
+{
+	struct arm_smmu_master_domain *master_domain = state->old_master_domain;
+	struct arm_smmu_master *master = state->master;
+
+	iommu_group_mutex_assert(master->dev);
+
+	if (!master_domain)
+		return;
+
 	arm_smmu_disable_iopf(master, master_domain);
 	kfree(master_domain);
+	state->old_master_domain = NULL;
 }
 
 /*
@@ -3609,7 +3625,8 @@ void arm_smmu_attach_commit(struct arm_smmu_attach_state *state)
 		arm_smmu_atc_inv_master(master, IOMMU_NO_PASID);
 	}
 
-	arm_smmu_remove_master_domain(master, state->old_domain, state->ssid);
+	state->old_master_domain = arm_smmu_remove_master_domain(
+		master, state->old_domain, state->ssid);
 	arm_smmu_install_old_domain_invs(state);
 	master->ats_enabled = state->ats_enabled;
 }
@@ -3684,6 +3701,7 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev,
 
 	arm_smmu_attach_commit(&state);
 	mutex_unlock(&arm_smmu_asid_lock);
+	arm_smmu_attach_release(&state);
 	return 0;
 }
 
@@ -3766,8 +3784,10 @@ int arm_smmu_set_pasid(struct arm_smmu_master *master,
 
 	mutex_lock(&arm_smmu_asid_lock);
 	ret = arm_smmu_attach_prepare(&state, &smmu_domain->domain);
-	if (ret)
-		goto out_unlock;
+	if (ret) {
+		mutex_unlock(&arm_smmu_asid_lock);
+		return ret;
+	}
 
 	/*
 	 * We don't want to obtain to the asid_lock too early, so fix up the
@@ -3781,10 +3801,9 @@ int arm_smmu_set_pasid(struct arm_smmu_master *master,
 	arm_smmu_update_ste(master, sid_domain, state.ats_enabled);
 
 	arm_smmu_attach_commit(&state);
-
-out_unlock:
 	mutex_unlock(&arm_smmu_asid_lock);
-	return ret;
+	arm_smmu_attach_release(&state);
+	return 0;
 }
 
 static int arm_smmu_blocking_set_dev_pasid(struct iommu_domain *new_domain,
@@ -3804,9 +3823,11 @@ static int arm_smmu_blocking_set_dev_pasid(struct iommu_domain *new_domain,
 	arm_smmu_clear_cd(master, pasid);
 	if (master->ats_enabled)
 		arm_smmu_atc_inv_master(master, pasid);
-	arm_smmu_remove_master_domain(master, &smmu_domain->domain, pasid);
+	state.old_master_domain = arm_smmu_remove_master_domain(
+		master, &smmu_domain->domain, pasid);
 	arm_smmu_install_old_domain_invs(&state);
 	mutex_unlock(&arm_smmu_asid_lock);
+	arm_smmu_attach_release(&state);
 
 	/*
 	 * When the last user of the CD table goes away downgrade the STE back
@@ -3869,6 +3890,7 @@ static void arm_smmu_attach_dev_ste(struct iommu_domain *domain,
 	arm_smmu_install_ste_for_dev(master, ste);
 	arm_smmu_attach_commit(&state);
 	mutex_unlock(&arm_smmu_asid_lock);
+	arm_smmu_attach_release(&state);
 
 	/*
 	 * This has to be done after removing the master from the
-- 
2.43.0