linux-kernel - [PATCH v4 10/13] iommu/arm-smmu-v3-sva: Remove bond refcount

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Message-ID: <20230621063825.268890-11-mshavit@google.com>
Date:   Wed, 21 Jun 2023 14:37:22 +0800
From:   Michael Shavit <mshavit@...gle.com>
To:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>
Cc:     Michael Shavit <mshavit@...gle.com>, jean-philippe@...aro.org,
        nicolinc@...dia.com, jgg@...dia.com, baolu.lu@...ux.intel.com,
        linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: [PATCH v4 10/13] iommu/arm-smmu-v3-sva: Remove bond refcount

The iommu-sva framework checks if a bond between a device and mm already
exists and handles refcounting at the iommu_domain level.
__arm_smmu_sva_bind is therefore only called once for a device/mm pair.

Signed-off-by: Michael Shavit <mshavit@...gle.com>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c | 12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

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 d07c08b53c5cf..20301d0a2c0b0 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
@@ -29,7 +29,6 @@ struct arm_smmu_bond {
 	struct mm_struct		*mm;
 	struct arm_smmu_mmu_notifier	*smmu_mn;
 	struct list_head		list;
-	refcount_t			refs;
 };
 
 #define sva_to_bond(handle) \
@@ -377,21 +376,12 @@ __arm_smmu_sva_bind(struct device *dev, struct mm_struct *mm)
 	if (!master || !master->sva_enabled)
 		return ERR_PTR(-ENODEV);
 
-	/* If bind() was already called for this {dev, mm} pair, reuse it. */
-	list_for_each_entry(bond, &master->bonds, list) {
-		if (bond->mm == mm) {
-			refcount_inc(&bond->refs);
-			return &bond->sva;
-		}
-	}
-
 	bond = kzalloc(sizeof(*bond), GFP_KERNEL);
 	if (!bond)
 		return ERR_PTR(-ENOMEM);
 
 	bond->mm = mm;
 	bond->sva.dev = dev;
-	refcount_set(&bond->refs, 1);
 
 	bond->smmu_mn = arm_smmu_mmu_notifier_get(smmu_domain, mm);
 	if (IS_ERR(bond->smmu_mn)) {
@@ -570,7 +560,7 @@ void arm_smmu_sva_remove_dev_pasid(struct iommu_domain *domain,
 		}
 	}
 
-	if (!WARN_ON(!bond) && refcount_dec_and_test(&bond->refs)) {
+	if (!WARN_ON(!bond)) {
 		list_del(&bond->list);
 		arm_smmu_mmu_notifier_put(bond->smmu_mn);
 		kfree(bond);
-- 
2.41.0.162.gfafddb0af9-goog