[PATCH rfcv1 5/8] iommu/arm-smmu-v3: Pre-allocate a per-master invalidation array

Nicolin Chen
2025-08-14T01:26:27Z

When a master is attached from an old domain to a new domain, it needs to
build an invalidation array to delete and add the array entries from/onto
the invalidation arrays of those two domains, passed via the del_invs and
add_invs arguments in to arm_smmu_invs_del/add() respectively.

Since the master->num_streams might differ across masters, a memory would
have to be allocated when building an add_invs/del_invs array which might
fail with -ENOMEM.

On the other hand, an attachment to arm_smmu_blocked_domain must not fail
so it's the best to avoid any memory allocation in that path.

Pre-allocate a fixed size invalidation array for every master. This array
will be filled dynamically when building an add_invs or del_invs array to
attach or detach an smmu_domain.

Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 1 +
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 10 ++++++++++
2 files changed, 11 insertions(+)

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 d7421b56e3598..0330444bef45f 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -919,6 +919,7 @@ struct arm_smmu_master {
struct arm_smmu_device *smmu;
struct device *dev;
struct arm_smmu_stream *streams;
+ struct arm_smmu_invs *invs;
struct arm_smmu_vmaster *vmaster; /* use smmu->streams_mutex */
/* Locked by the iommu core using the group mutex */
struct arm_smmu_ctx_desc_cfg cd_table;
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 73f3b411ff7ef..fb5429d8ebb29 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -3723,6 +3723,7 @@ static int arm_smmu_insert_master(struct arm_smmu_device *smmu,
int i;
int ret = 0;
struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(master->dev);
+ size_t num_ats = dev_is_pci(master->dev) ? master->num_streams : 0;

master->streams = kcalloc(fwspec->num_ids, sizeof(*master->streams),
GFP_KERNEL);
@@ -3730,6 +3731,13 @@ static int arm_smmu_insert_master(struct arm_smmu_device *smmu,
return -ENOMEM;
master->num_streams = fwspec->num_ids;

+ /* Max possible num_invs: two for ASID/VMIDs and num_ats for ATC_INVs */
+ master->invs = arm_smmu_invs_alloc(2 + num_ats);
+ if (IS_ERR(master->invs)) {
+ kfree(master->streams);
+ return PTR_ERR(master->invs);
+ }
+
mutex_lock(&smmu->streams_mutex);
for (i = 0; i < fwspec->num_ids; i++) {
struct arm_smmu_stream *new_stream = &master->streams[i];
@@ -3767,6 +3775,7 @@ static int arm_smmu_insert_master(struct arm_smmu_device *smmu,
for (i--; i >= 0; i--)
rb_erase(&master->streams[i].node, &smmu->streams);
kfree(master->streams);
+ kfree(master->invs);
}
mutex_unlock(&smmu->streams_mutex);

@@ -3788,6 +3797,7 @@ static void arm_smmu_remove_master(struct arm_smmu_master *master)
mutex_unlock(&smmu->streams_mutex);

kfree(master->streams);
+ kfree(master->invs);
}

static struct iommu_device *arm_smmu_probe_device(struct device *dev)
--
2.43.0