[PATCH v4 02/10] iommu/arm-smmu-v3: Pass in arm_smmu_make_cd_fn to arm_smmu_set_pasid()

Nicolin Chen
2026-03-19T19:52:49Z

To install a domain (CD) to a substream, the common flow in the driver is:
- Make an S1 or SVA CD outside arm_smmu_asid_lock
- Invoke arm_smmu_set_pasid() where it takes arm_smmu_asid_lock, and fix
the ASID in the CD.

The reason for such a flow is for the timing of arm_smmu_asid_lock, since
it was too early to take the mutex outside the function.

Tidy it up by passing in a function pointer for CD making,, which supports
both existing functions: arm_smmu_make_s1_cd() and arm_smmu_make_sva_cd().

Then arm_smmu_set_pasid() can make a CD inside the lock where ASID is safe
to access.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 7 ++++++-
.../iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c | 4 ++--
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 19 ++++---------------
3 files changed, 12 insertions(+), 18 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 dd5d2b5acf664..a31f9f7f39d3a 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -1076,9 +1076,14 @@ void arm_smmu_write_cd_entry(struct arm_smmu_master *master, int ssid,
struct arm_smmu_cd *cdptr,
const struct arm_smmu_cd *target);

+typedef void (*arm_smmu_make_cd_fn)(struct arm_smmu_cd *target,
+ struct arm_smmu_master *master,
+ struct arm_smmu_domain *smmu_domain);
+
int arm_smmu_set_pasid(struct arm_smmu_master *master,
struct arm_smmu_domain *smmu_domain, ioasid_t pasid,
- struct arm_smmu_cd *cd, struct iommu_domain *old);
+ struct arm_smmu_cd *cd, struct iommu_domain *old,
+ arm_smmu_make_cd_fn make_cd_fn);

void arm_smmu_domain_inv_range(struct arm_smmu_domain *smmu_domain,
unsigned long iova, size_t size,
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
index 414fc899140f7..4370cb88c57cf 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
@@ -273,8 +273,8 @@ static int arm_smmu_sva_set_dev_pasid(struct iommu_domain *domain,
* This does not need the arm_smmu_asid_lock because SVA domains never
* get reassigned
*/
- arm_smmu_make_sva_cd(&target, master, smmu_domain);
- ret = arm_smmu_set_pasid(master, smmu_domain, id, &target, old);
+ ret = arm_smmu_set_pasid(master, smmu_domain, id, &target, old,
+ arm_smmu_make_sva_cd);

mmput(domain->mm);
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 01030ffd2fe23..78d45952db7da 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -3738,13 +3738,8 @@ static int arm_smmu_s1_set_dev_pasid(struct iommu_domain *domain,
if (smmu_domain->stage != ARM_SMMU_DOMAIN_S1)
return -EINVAL;

- /*
- * We can read cd.asid outside the lock because arm_smmu_set_pasid()
- * will fix it
- */
- arm_smmu_make_s1_cd(&target_cd, master, smmu_domain);
return arm_smmu_set_pasid(master, to_smmu_domain(domain), id,
- &target_cd, old);
+ &target_cd, old, arm_smmu_make_s1_cd);
}

static void arm_smmu_update_ste(struct arm_smmu_master *master,
@@ -3774,7 +3769,8 @@ static void arm_smmu_update_ste(struct arm_smmu_master *master,

int arm_smmu_set_pasid(struct arm_smmu_master *master,
struct arm_smmu_domain *smmu_domain, ioasid_t pasid,
- struct arm_smmu_cd *cd, struct iommu_domain *old)
+ struct arm_smmu_cd *cd, struct iommu_domain *old,
+ arm_smmu_make_cd_fn make_cd_fn)
{
struct iommu_domain *sid_domain =
iommu_driver_get_domain_for_dev(master->dev);
@@ -3805,14 +3801,7 @@ int arm_smmu_set_pasid(struct arm_smmu_master *master,
if (ret)
goto out_unlock;

- /*
- * We don't want to obtain to the asid_lock too early, so fix up the
- * caller set ASID under the lock in case it changed.
- */
- cd->data[0] &= ~cpu_to_le64(CTXDESC_CD_0_ASID);
- cd->data[0] |= cpu_to_le64(
- FIELD_PREP(CTXDESC_CD_0_ASID, smmu_domain->cd.asid));
-
+ make_cd_fn(cd, master, smmu_domain);
arm_smmu_write_cd_entry(master, pasid, cdptr, cd);
arm_smmu_update_ste(master, sid_domain, state.ats_enabled);

--
2.43.0