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From: Lu Baolu <baolu.lu@linux.intel.com>
To: iommu@lists.linux-foundation.org, iommu@lists.linux.dev
Cc: Kevin Tian <kevin.tian@intel.com>,
	Ashok Raj <ashok.raj@intel.com>, Liu Yi L <yi.l.liu@intel.com>,
	Jacob jun Pan <jacob.jun.pan@intel.com>,
	linux-kernel@vger.kernel.org, Lu Baolu <baolu.lu@linux.intel.com>
Subject: [PATCH v4 04/11] iommu/vt-d: Unnecessary spinlock for root table alloc and free
Date: Wed,  6 Jul 2022 10:55:17 +0800	[thread overview]
Message-ID: <20220706025524.2904370-5-baolu.lu@linux.intel.com> (raw)
In-Reply-To: <20220706025524.2904370-1-baolu.lu@linux.intel.com>

The IOMMU root table is allocated and freed in the IOMMU initialization
code in static boot or hot-remove paths. There's no need for a spinlock.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
---
 drivers/iommu/intel/iommu.c | 18 +++++-------------
 1 file changed, 5 insertions(+), 13 deletions(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 77915d61f7ec..ff49c9460ede 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -809,14 +809,12 @@ static int device_context_mapped(struct intel_iommu *iommu, u8 bus, u8 devfn)
 
 static void free_context_table(struct intel_iommu *iommu)
 {
-	int i;
-	unsigned long flags;
 	struct context_entry *context;
+	int i;
+
+	if (!iommu->root_entry)
+		return;
 
-	spin_lock_irqsave(&iommu->lock, flags);
-	if (!iommu->root_entry) {
-		goto out;
-	}
 	for (i = 0; i < ROOT_ENTRY_NR; i++) {
 		context = iommu_context_addr(iommu, i, 0, 0);
 		if (context)
@@ -828,12 +826,10 @@ static void free_context_table(struct intel_iommu *iommu)
 		context = iommu_context_addr(iommu, i, 0x80, 0);
 		if (context)
 			free_pgtable_page(context);
-
 	}
+
 	free_pgtable_page(iommu->root_entry);
 	iommu->root_entry = NULL;
-out:
-	spin_unlock_irqrestore(&iommu->lock, flags);
 }
 
 #ifdef CONFIG_DMAR_DEBUG
@@ -1232,7 +1228,6 @@ static void domain_unmap(struct dmar_domain *domain, unsigned long start_pfn,
 static int iommu_alloc_root_entry(struct intel_iommu *iommu)
 {
 	struct root_entry *root;
-	unsigned long flags;
 
 	root = (struct root_entry *)alloc_pgtable_page(iommu->node);
 	if (!root) {
@@ -1242,10 +1237,7 @@ static int iommu_alloc_root_entry(struct intel_iommu *iommu)
 	}
 
 	__iommu_flush_cache(iommu, root, ROOT_SIZE);
-
-	spin_lock_irqsave(&iommu->lock, flags);
 	iommu->root_entry = root;
-	spin_unlock_irqrestore(&iommu->lock, flags);
 
 	return 0;
 }
-- 
2.25.1


WARNING: multiple messages have this Message-ID (diff)
From: Lu Baolu <baolu.lu@linux.intel.com>
To: iommu@lists.linux-foundation.org, iommu@lists.linux.dev
Cc: Kevin Tian <kevin.tian@intel.com>,
	Ashok Raj <ashok.raj@intel.com>,
	linux-kernel@vger.kernel.org,
	Jacob jun Pan <jacob.jun.pan@intel.com>
Subject: [PATCH v4 04/11] iommu/vt-d: Unnecessary spinlock for root table alloc and free
Date: Wed,  6 Jul 2022 10:55:17 +0800	[thread overview]
Message-ID: <20220706025524.2904370-5-baolu.lu@linux.intel.com> (raw)
In-Reply-To: <20220706025524.2904370-1-baolu.lu@linux.intel.com>

The IOMMU root table is allocated and freed in the IOMMU initialization
code in static boot or hot-remove paths. There's no need for a spinlock.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
---
 drivers/iommu/intel/iommu.c | 18 +++++-------------
 1 file changed, 5 insertions(+), 13 deletions(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 77915d61f7ec..ff49c9460ede 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -809,14 +809,12 @@ static int device_context_mapped(struct intel_iommu *iommu, u8 bus, u8 devfn)
 
 static void free_context_table(struct intel_iommu *iommu)
 {
-	int i;
-	unsigned long flags;
 	struct context_entry *context;
+	int i;
+
+	if (!iommu->root_entry)
+		return;
 
-	spin_lock_irqsave(&iommu->lock, flags);
-	if (!iommu->root_entry) {
-		goto out;
-	}
 	for (i = 0; i < ROOT_ENTRY_NR; i++) {
 		context = iommu_context_addr(iommu, i, 0, 0);
 		if (context)
@@ -828,12 +826,10 @@ static void free_context_table(struct intel_iommu *iommu)
 		context = iommu_context_addr(iommu, i, 0x80, 0);
 		if (context)
 			free_pgtable_page(context);
-
 	}
+
 	free_pgtable_page(iommu->root_entry);
 	iommu->root_entry = NULL;
-out:
-	spin_unlock_irqrestore(&iommu->lock, flags);
 }
 
 #ifdef CONFIG_DMAR_DEBUG
@@ -1232,7 +1228,6 @@ static void domain_unmap(struct dmar_domain *domain, unsigned long start_pfn,
 static int iommu_alloc_root_entry(struct intel_iommu *iommu)
 {
 	struct root_entry *root;
-	unsigned long flags;
 
 	root = (struct root_entry *)alloc_pgtable_page(iommu->node);
 	if (!root) {
@@ -1242,10 +1237,7 @@ static int iommu_alloc_root_entry(struct intel_iommu *iommu)
 	}
 
 	__iommu_flush_cache(iommu, root, ROOT_SIZE);
-
-	spin_lock_irqsave(&iommu->lock, flags);
 	iommu->root_entry = root;
-	spin_unlock_irqrestore(&iommu->lock, flags);
 
 	return 0;
 }
-- 
2.25.1

_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  parent reply	other threads:[~2022-07-06  3:00 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-07-06  2:55 [PATCH v4 00/11] iommu/vt-d: Optimize the use of locks Lu Baolu
2022-07-06  2:55 ` Lu Baolu
2022-07-06  2:55 ` [PATCH v4 01/11] iommu/vt-d: debugfs: Remove device_domain_lock usage Lu Baolu
2022-07-06  2:55   ` Lu Baolu
     [not found]   ` <849557ab-9c1b-a2ff-6fc6-6564f38d1187@linux.intel.com>
2022-07-07  9:18     ` Baolu Lu
2022-07-06  2:55 ` [PATCH v4 02/11] iommu/vt-d: Remove clearing translation data in disable_dmar_iommu() Lu Baolu
2022-07-06  2:55   ` Lu Baolu
2022-07-07  3:03   ` Tian, Kevin
2022-07-06  2:55 ` [PATCH v4 03/11] iommu/vt-d: Use pci_get_domain_bus_and_slot() in pgtable_walk() Lu Baolu
2022-07-06  2:55   ` Lu Baolu
2022-07-06  2:55 ` Lu Baolu [this message]
2022-07-06  2:55   ` [PATCH v4 04/11] iommu/vt-d: Unnecessary spinlock for root table alloc and free Lu Baolu
2022-07-06  2:55 ` [PATCH v4 05/11] iommu/vt-d: Replace spin_lock_irqsave() with spin_lock() Lu Baolu
2022-07-06  2:55   ` Lu Baolu
2022-07-06  2:55 ` [PATCH v4 06/11] iommu/vt-d: Acquiring lock in domain ID allocation helpers Lu Baolu
2022-07-06  2:55   ` Lu Baolu
2022-07-06  2:55 ` [PATCH v4 07/11] iommu/vt-d: Acquiring lock in pasid manipulation helpers Lu Baolu
2022-07-06  2:55   ` Lu Baolu
2022-07-06  2:55 ` [PATCH v4 08/11] iommu/vt-d: Check device list of domain in domain free path Lu Baolu
2022-07-06  2:55   ` Lu Baolu
2022-07-06  2:55 ` [PATCH v4 09/11] iommu/vt-d: Fold __dmar_remove_one_dev_info() into its caller Lu Baolu
2022-07-06  2:55   ` Lu Baolu
2022-07-06  2:55 ` [PATCH v4 10/11] iommu/vt-d: Use device_domain_lock accurately Lu Baolu
2022-07-06  2:55   ` Lu Baolu
2022-07-06  2:55 ` [PATCH v4 11/11] iommu/vt-d: Convert global spinlock into per domain lock Lu Baolu
2022-07-06  2:55   ` Lu Baolu

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