linux-kernel - [PATCH 03/12] iommu/vt-d: Remove users from intel_svm

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Date:   Tue, 31 Jan 2023 15:37:31 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     kan.liang@...ux.intel.com, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: [PATCH 03/12] iommu/vt-d: Remove users from intel_svm_dev

It was used as a reference counter of an existing bond between device
and user application memory address. Commit be51b1d6bbff ("iommu/sva:
Refactoring iommu_sva_bind/unbind_device()") has added this in iommu
core. Remove it to avoid duplicate code.

Reviewed-by: Kevin Tian <kevin.tian@...el.com>
Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
Link: https://lore.kernel.org/r/20230109014955.147068-4-baolu.lu@linux.intel.com
---
 drivers/iommu/intel/iommu.h |  1 -
 drivers/iommu/intel/svm.c   | 62 ++++++++++++++++---------------------
 2 files changed, 27 insertions(+), 36 deletions(-)

diff --git a/drivers/iommu/intel/iommu.h b/drivers/iommu/intel/iommu.h
index e7c732979364..2a1619ff0d79 100644
--- a/drivers/iommu/intel/iommu.h
+++ b/drivers/iommu/intel/iommu.h
@@ -762,7 +762,6 @@ struct intel_svm_dev {
 	struct device *dev;
 	struct intel_iommu *iommu;
 	struct iommu_sva sva;
-	int users;
 	u16 did;
 	u16 sid, qdep;
 };
diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
index d1e445f03aa6..c7dc53e40c26 100644
--- a/drivers/iommu/intel/svm.c
+++ b/drivers/iommu/intel/svm.c
@@ -333,13 +333,6 @@ static struct iommu_sva *intel_svm_bind_mm(struct intel_iommu *iommu,
 		}
 	}
 
-	/* Find the matching device in svm list */
-	sdev = svm_lookup_device_by_dev(svm, dev);
-	if (sdev) {
-		sdev->users++;
-		goto success;
-	}
-
 	sdev = kzalloc(sizeof(*sdev), GFP_KERNEL);
 	if (!sdev) {
 		ret = -ENOMEM;
@@ -350,7 +343,6 @@ static struct iommu_sva *intel_svm_bind_mm(struct intel_iommu *iommu,
 	sdev->iommu = iommu;
 	sdev->did = FLPT_DEFAULT_DID;
 	sdev->sid = PCI_DEVID(info->bus, info->devfn);
-	sdev->users = 1;
 	sdev->sva.dev = dev;
 	init_rcu_head(&sdev->rcu);
 	if (info->ats_enabled) {
@@ -367,7 +359,7 @@ static struct iommu_sva *intel_svm_bind_mm(struct intel_iommu *iommu,
 		goto free_sdev;
 
 	list_add_rcu(&sdev->list, &svm->devs);
-success:
+
 	return &sdev->sva;
 
 free_sdev:
@@ -401,32 +393,32 @@ static int intel_svm_unbind_mm(struct device *dev, u32 pasid)
 	mm = svm->mm;
 
 	if (sdev) {
-		sdev->users--;
-		if (!sdev->users) {
-			list_del_rcu(&sdev->list);
-			/* Flush the PASID cache and IOTLB for this device.
-			 * Note that we do depend on the hardware *not* using
-			 * the PASID any more. Just as we depend on other
-			 * devices never using PASIDs that they have no right
-			 * to use. We have a *shared* PASID table, because it's
-			 * large and has to be physically contiguous. So it's
-			 * hard to be as defensive as we might like. */
-			intel_pasid_tear_down_entry(iommu, dev,
-						    svm->pasid, false);
-			intel_svm_drain_prq(dev, svm->pasid);
-			kfree_rcu(sdev, rcu);
-
-			if (list_empty(&svm->devs)) {
-				if (svm->notifier.ops)
-					mmu_notifier_unregister(&svm->notifier, mm);
-				pasid_private_remove(svm->pasid);
-				/* We mandate that no page faults may be outstanding
-				 * for the PASID when intel_svm_unbind_mm() is called.
-				 * If that is not obeyed, subtle errors will happen.
-				 * Let's make them less subtle... */
-				memset(svm, 0x6b, sizeof(*svm));
-				kfree(svm);
-			}
+		list_del_rcu(&sdev->list);
+		/*
+		 * Flush the PASID cache and IOTLB for this device.
+		 * Note that we do depend on the hardware *not* using
+		 * the PASID any more. Just as we depend on other
+		 * devices never using PASIDs that they have no right
+		 * to use. We have a *shared* PASID table, because it's
+		 * large and has to be physically contiguous. So it's
+		 * hard to be as defensive as we might like.
+		 */
+		intel_pasid_tear_down_entry(iommu, dev, svm->pasid, false);
+		intel_svm_drain_prq(dev, svm->pasid);
+		kfree_rcu(sdev, rcu);
+
+		if (list_empty(&svm->devs)) {
+			if (svm->notifier.ops)
+				mmu_notifier_unregister(&svm->notifier, mm);
+			pasid_private_remove(svm->pasid);
+			/*
+			 * We mandate that no page faults may be outstanding
+			 * for the PASID when intel_svm_unbind_mm() is called.
+			 * If that is not obeyed, subtle errors will happen.
+			 * Let's make them less subtle...
+			 */
+			memset(svm, 0x6b, sizeof(*svm));
+			kfree(svm);
 		}
 	}
 out:
-- 
2.34.1