linux-kernel - [PATCH v2 08/10] iommu/arm-smmu-v3: Introduce INV_TYPE_S2_VMID

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Message-ID: <58bda77b3965ca6d8871ca242f01bb50d2baf75b.1769044718.git.nicolinc@nvidia.com>
Date: Wed, 21 Jan 2026 17:24:26 -0800
From: Nicolin Chen <nicolinc@...dia.com>
To: <will@...nel.org>, <robin.murphy@....com>, <jgg@...dia.com>
CC: <joro@...tes.org>, <jpb@...nel.org>, <praan@...gle.com>,
	<miko.lenczewski@....com>, <linux-arm-kernel@...ts.infradead.org>,
	<iommu@...ts.linux.dev>, <linux-kernel@...r.kernel.org>,
	<patches@...ts.linux.dev>
Subject: [PATCH v2 08/10] iommu/arm-smmu-v3: Introduce INV_TYPE_S2_VMID_VSMMU

A VMID held by a vSMMU is required to setup hardware (e.g. tegra241-cmdqv)
during its initialization. So, it should be allocated in the ->viommu_init
callback. This makes the VMID lifecycle unique than a VMID allocated for a
naked S2 attachment.

Introduce an INV_TYPE_S2_VMID_VSMMU to accommodate this case.

Note that a second device attaching to a nested domain associated with the
same vSMMU instance will have an INV_TYPE_S2_VMID_VSMMU and reuse the VMID
held by the vSMMU. Devices attaching directly to the nesting parent domain
will have an INV_TYPE_S2_VMID and shouldn't resue the VMID from the vSMMU.

Suggested-by: Jason Gunthorpe <jgg@...dia.com>
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 | 18 +++++++++++++++---
 2 files changed, 16 insertions(+), 3 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 386ac75879c0..8365660282d5 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -656,6 +656,7 @@ struct arm_smmu_cmdq_batch {
 enum arm_smmu_inv_type {
 	INV_TYPE_S1_ASID,
 	INV_TYPE_S2_VMID,
+	INV_TYPE_S2_VMID_VSMMU,
 	INV_TYPE_S2_VMID_S1_CLEAR,
 	INV_TYPE_ATS,
 	INV_TYPE_ATS_FULL,
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 8323f74c8923..6d3da3f82ec8 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -1904,7 +1904,8 @@ void arm_smmu_make_s2_domain_ste(struct arm_smmu_ste *target,
 	u64 vtcr_val;
 	struct arm_smmu_device *smmu = master->smmu;
 
-	WARN_ON(tag->type != INV_TYPE_S2_VMID);
+	WARN_ON(tag->type != INV_TYPE_S2_VMID &&
+		tag->type != INV_TYPE_S2_VMID_VSMMU);
 
 	memset(target, 0, sizeof(*target));
 	target->data[0] = cpu_to_le64(
@@ -2592,6 +2593,7 @@ static void __arm_smmu_domain_inv_range(struct arm_smmu_invs *invs,
 						   granule);
 			break;
 		case INV_TYPE_S2_VMID:
+		case INV_TYPE_S2_VMID_VSMMU:
 			cmd.tlbi.vmid = cur->id;
 			cmd.tlbi.leaf = leaf;
 			arm_smmu_inv_to_cmdq_batch(cur, &cmds, &cmd, iova, size,
@@ -3149,7 +3151,10 @@ int arm_smmu_domain_get_iotlb_tag(struct arm_smmu_domain *smmu_domain,
 		tag->type = INV_TYPE_S1_ASID;
 		break;
 	case ARM_SMMU_DOMAIN_S2:
-		tag->type = INV_TYPE_S2_VMID;
+		if (vsmmu)
+			tag->type = INV_TYPE_S2_VMID_VSMMU;
+		else
+			tag->type = INV_TYPE_S2_VMID;
 		break;
 	default:
 		return -EINVAL;
@@ -3163,6 +3168,12 @@ int arm_smmu_domain_get_iotlb_tag(struct arm_smmu_domain *smmu_domain,
 		return ret;
 
 	/* Allocate a new IOTLB cache tag (users counter == 0) */
+	if (tag->type == INV_TYPE_S2_VMID_VSMMU) {
+		/* Use the pre-allocated VMID from vSMMU */
+		tag->id = vsmmu->vmid;
+		return 0;
+	}
+
 	lockdep_assert_held(&arm_smmu_asid_lock);
 
 	if (tag->type == INV_TYPE_S1_ASID) {
@@ -3233,6 +3244,7 @@ arm_smmu_master_build_inv(struct arm_smmu_master *master,
 		}
 		break;
 	case INV_TYPE_S2_VMID:
+	case INV_TYPE_S2_VMID_VSMMU:
 		cur->size_opcode = CMDQ_OP_TLBI_S2_IPA;
 		cur->nsize_opcode = CMDQ_OP_TLBI_S12_VMALL;
 		break;
@@ -3280,7 +3292,7 @@ arm_smmu_master_build_invs(struct arm_smmu_master *master, bool ats_enabled,
 		return NULL;
 
 	/* All the nested S1 ASIDs have to be flushed when S2 parent changes */
-	if (nesting) {
+	if (tag->type == INV_TYPE_S2_VMID_VSMMU) {
 		if (!arm_smmu_master_build_inv(master,
 					       INV_TYPE_S2_VMID_S1_CLEAR,
 					       tag->id, IOMMU_NO_PASID, 0))
-- 
2.43.0