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

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Message-ID: <2b55869f698340d5791210b9a7e542f81ad20bcb.1755131672.git.nicolinc@nvidia.com>
Date: Wed, 13 Aug 2025 18:25:36 -0700
From: Nicolin Chen <nicolinc@...dia.com>
To: <jgg@...dia.com>, <will@...nel.org>, <robin.murphy@....com>
CC: <joro@...tes.org>, <jean-philippe@...aro.org>, <miko.lenczewski@....com>,
	<balbirs@...dia.com>, <peterz@...radead.org>, <smostafa@...gle.com>,
	<kevin.tian@...el.com>, <praan@...gle.com>, <zhangzekun11@...wei.com>,
	<linux-arm-kernel@...ts.infradead.org>, <iommu@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>, <patches@...ts.linux.dev>
Subject: [PATCH rfcv1 5/8] iommu/arm-smmu-v3: Pre-allocate a per-master invalidation array

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@...dia.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