[RFC PATCH v4 04/16] iommu/arm-smmu-v3: Track realm pSMMU users with refcount_t
Aneesh Kumar K.V (Arm)
aneesh.kumar at kernel.org
Mon Apr 27 01:53:32 PDT 2026
Replace the realm pSMMU active-state boolean with a refcount so
activation/deactivation is tied to actual Realm vIOMMU lifetime.
- add realm_mutex and realm_users (refcount_t) to struct arm_smmu_device
- on first Realm init, activate pSMMU and set realm_users to 1
- on subsequent Realm inits, increment realm_users
- on Realm viommu destroy, decrement realm_users and call
rmi_psmmu_deactivate() when the last user drops the count to 0
This removes duplicated state tracking and ensures pSMMU is deactivated only
after the last Realm user is gone.
Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar at kernel.org>
---
arch/arm64/include/asm/rmi_cmds.h | 1 +
arch/arm64/kernel/rmi.c | 12 ++++++
.../iommu/arm/arm-smmu-v3/arm-smmu-v3-realm.c | 39 +++++++++++++++----
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 3 +-
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 4 +-
5 files changed, 50 insertions(+), 9 deletions(-)
diff --git a/arch/arm64/include/asm/rmi_cmds.h b/arch/arm64/include/asm/rmi_cmds.h
index 659d68ad5f1d..205fc200d1db 100644
--- a/arch/arm64/include/asm/rmi_cmds.h
+++ b/arch/arm64/include/asm/rmi_cmds.h
@@ -865,6 +865,7 @@ static inline unsigned long rmi_psmmu_event_consume(unsigned long psmmu_phys,
int rmi_psmmu_activate(unsigned long psmmu_phys,
unsigned long psmmu_params_phys, unsigned long *rmi_ret);
+int rmi_psmmu_deactivate(unsigned long psmmu_phys, unsigned long *rmi_ret);
int rmi_psmmu_st_l2_create(unsigned long psmmu_phys,
unsigned long stream_id, unsigned long *rmi_ret);
int rmi_psmmu_st_l2_destroy(unsigned long psmmu_phys,
diff --git a/arch/arm64/kernel/rmi.c b/arch/arm64/kernel/rmi.c
index cc4050db5a6a..884ab3f99f2f 100644
--- a/arch/arm64/kernel/rmi.c
+++ b/arch/arm64/kernel/rmi.c
@@ -436,6 +436,18 @@ int rmi_psmmu_activate(unsigned long psmmu_phys,
return 0;
}
+int rmi_psmmu_deactivate(unsigned long psmmu_phys, unsigned long *rmi_ret)
+{
+ struct rmi_sro_state *sro __free(sro) =
+ rmi_sro_init(SMC_RMI_PSMMU_DEACTIVATE, psmmu_phys);
+ if (!sro)
+ return -ENOMEM;
+
+ *rmi_ret = rmi_sro_execute(sro);
+
+ return 0;
+}
+
int rmi_psmmu_st_l2_create(unsigned long psmmu_phys,
unsigned long stream_id, unsigned long *rmi_ret)
{
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-realm.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-realm.c
index 6f8de7cead9d..dfff493f96d0 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-realm.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-realm.c
@@ -124,9 +124,25 @@ void arm_smmu_setup_realm_irqs(struct arm_smmu_device *smmu)
}
}
+static bool arm_realm_smmu_active(struct arm_smmu_device *smmu)
+{
+ lockdep_assert_held(&smmu->realm_mutex);
+ return refcount_read(&smmu->realm_users) > 0;
+}
+
static void arm_realm_smmu_v3_destroy(struct iommufd_viommu *viommu)
{
- /* When we add refcount psmmu deactivate here. */
+ unsigned long rmi_ret;
+ struct arm_smmu_device *smmu =
+ container_of(viommu->iommu_dev, struct arm_smmu_device, iommu);
+
+ guard(mutex)(&smmu->realm_mutex);
+ if (WARN_ON(!arm_realm_smmu_active(smmu)))
+ return;
+
+ if (refcount_dec_and_test(&smmu->realm_users) &&
+ (rmi_psmmu_deactivate(smmu->base_phys, &rmi_ret) || rmi_ret))
+ dev_warn(smmu->dev, "failed to deactivate realm pSMMU\n");
}
static void arm_realm_smmu_v3_vdevice_destroy(struct iommufd_vdevice *vdev)
@@ -140,7 +156,8 @@ static void arm_realm_smmu_v3_vdevice_destroy(struct iommufd_vdevice *vdev)
unsigned long rmi_ret = 0;
int ret;
- if (!smmu->realm_initialized)
+ guard(mutex)(&smmu->realm_mutex);
+ if (!arm_realm_smmu_active(smmu))
return;
ret = rmi_psmmu_st_l2_destroy(smmu->base_phys,
@@ -168,7 +185,8 @@ static int arm_realm_smmu_v3_vdevice_init(struct iommufd_vdevice *vdev)
unsigned long rmi_ret = 0;
int ret;
- if (!smmu->realm_initialized)
+ guard(mutex)(&smmu->realm_mutex);
+ if (!arm_realm_smmu_active(smmu))
return -EINVAL;
ret = rmi_psmmu_st_l2_create(smmu->base_phys,
@@ -229,12 +247,17 @@ int arm_realm_smmu_v3_init(struct iommufd_viommu *viommu,
if (!(smmu->features & ARM_SMMU_FEAT_RME))
return -EOPNOTSUPP;
- if (smmu->realm_initialized)
+ mutex_lock(&smmu->realm_mutex);
+ if (arm_realm_smmu_active(smmu)) {
+ refcount_inc(&smmu->realm_users);
goto psmmu_already_active;
+ }
params = (struct rmi_psmmu_params *)get_zeroed_page(GFP_KERNEL);
- if (!params)
- return -ENOMEM;
+ if (!params) {
+ ret = -ENOMEM;
+ goto out_unlock;
+ }
/* No ATS and PRI support */
if (!(smmu->features & ARM_SMMU_FEAT_MSI))
@@ -261,12 +284,14 @@ int arm_realm_smmu_v3_init(struct iommufd_viommu *viommu,
dev_warn(smmu->dev, "failed to activate realm pSMMU\n");
ret = -EIO;
} else {
- smmu->realm_initialized = true;
+ refcount_set(&smmu->realm_users, 1);
}
out_free:
free_page((unsigned long)params);
psmmu_already_active:
if (!ret)
viommu->ops = &arm_realm_smmu_v3_ops;
+out_unlock:
+ mutex_unlock(&smmu->realm_mutex);
return ret;
}
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 1e3d4d682e32..e458c3818c34 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -3946,6 +3946,8 @@ static int arm_smmu_init_structures(struct arm_smmu_device *smmu)
int ret;
mutex_init(&smmu->streams_mutex);
+ mutex_init(&smmu->realm_mutex);
+ refcount_set(&smmu->realm_users, 0);
smmu->streams = RB_ROOT;
ret = arm_smmu_init_queues(smmu);
@@ -3956,7 +3958,6 @@ static int arm_smmu_init_structures(struct arm_smmu_device *smmu)
if (ret)
return ret;
- smmu->realm_initialized = false;
if (smmu->impl_ops && smmu->impl_ops->init_structures)
return smmu->impl_ops->init_structures(smmu);
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 d528b3212d38..b5d0e1341236 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -13,6 +13,7 @@
#include <linux/iommufd.h>
#include <linux/kernel.h>
#include <linux/mmzone.h>
+#include <linux/refcount.h>
#include <linux/sizes.h>
struct arm_smmu_device;
@@ -812,7 +813,8 @@ struct arm_smmu_device {
struct rb_root streams;
struct mutex streams_mutex;
- bool realm_initialized;
+ struct mutex realm_mutex;
+ refcount_t realm_users;
};
struct arm_smmu_stream {
--
2.43.0
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