[PATCH v3 10/11] iommu/vt-d: Use device_domain_lock accurately

[Lu Baolu]

The device_domain_lock is used to protect the device tracking list of
a domain. Remove unnecessary spin_lock/unlock()'s and move the necessary
ones around the list access.

Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
 drivers/iommu/intel/iommu.c | 61 ++++++++++++++-----------------------
 1 file changed, 23 insertions(+), 38 deletions(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 3038aafecff9..1783859b511a 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -534,16 +534,10 @@ static int domain_update_device_node(struct dmar_domain *domain)
 {
 	struct device_domain_info *info;
 	int nid = NUMA_NO_NODE;
+	unsigned long flags;
 
-	assert_spin_locked(&device_domain_lock);
-
-	if (list_empty(&domain->devices))
-		return NUMA_NO_NODE;
-
+	spin_lock_irqsave(&device_domain_lock, flags);
 	list_for_each_entry(info, &domain->devices, link) {
-		if (!info->dev)
-			continue;
-
 		/*
 		 * There could possibly be multiple device numa nodes as devices
 		 * within the same domain may sit behind different IOMMUs. There
@@ -554,6 +548,7 @@ static int domain_update_device_node(struct dmar_domain *domain)
 		if (nid != NUMA_NO_NODE)
 			break;
 	}
+	spin_unlock_irqrestore(&device_domain_lock, flags);
 
 	return nid;
 }
@@ -1376,23 +1371,24 @@ static void __iommu_flush_iotlb(struct intel_iommu *iommu, u16 did,
 }
 
 static struct device_domain_info *
-iommu_support_dev_iotlb (struct dmar_domain *domain, struct intel_iommu *iommu,
-			 u8 bus, u8 devfn)
+iommu_support_dev_iotlb(struct dmar_domain *domain, struct intel_iommu *iommu,
+			u8 bus, u8 devfn)
 {
 	struct device_domain_info *info;
-
-	assert_spin_locked(&device_domain_lock);
+	unsigned long flags;
 
 	if (!iommu->qi)
 		return NULL;
 
-	list_for_each_entry(info, &domain->devices, link)
+	spin_lock_irqsave(&device_domain_lock, flags);
+	list_for_each_entry(info, &domain->devices, link) {
 		if (info->iommu == iommu && info->bus == bus &&
 		    info->devfn == devfn) {
-			if (info->ats_supported && info->dev)
-				return info;
-			break;
+			spin_unlock_irqrestore(&device_domain_lock, flags);
+			return info->ats_supported ? info : NULL;
 		}
+	}
+	spin_unlock_irqrestore(&device_domain_lock, flags);
 
 	return NULL;
 }
@@ -1401,24 +1397,23 @@ static void domain_update_iotlb(struct dmar_domain *domain)
 {
 	struct device_domain_info *info;
 	bool has_iotlb_device = false;
+	unsigned long flags;
 
-	assert_spin_locked(&device_domain_lock);
-
-	list_for_each_entry(info, &domain->devices, link)
+	spin_lock_irqsave(&device_domain_lock, flags);
+	list_for_each_entry(info, &domain->devices, link) {
 		if (info->ats_enabled) {
 			has_iotlb_device = true;
 			break;
 		}
-
+	}
 	domain->has_iotlb_device = has_iotlb_device;
+	spin_unlock_irqrestore(&device_domain_lock, flags);
 }
 
 static void iommu_enable_dev_iotlb(struct device_domain_info *info)
 {
 	struct pci_dev *pdev;
 
-	assert_spin_locked(&device_domain_lock);
-
 	if (!info || !dev_is_pci(info->dev))
 		return;
 
@@ -1464,8 +1459,6 @@ static void iommu_disable_dev_iotlb(struct device_domain_info *info)
 {
 	struct pci_dev *pdev;
 
-	assert_spin_locked(&device_domain_lock);
-
 	if (!dev_is_pci(info->dev))
 		return;
 
@@ -1908,11 +1901,11 @@ static int domain_context_mapping_one(struct dmar_domain *domain,
 				      struct pasid_table *table,
 				      u8 bus, u8 devfn)
 {
+	struct device_domain_info *info =
+			iommu_support_dev_iotlb(domain, iommu, bus, devfn);
 	u16 did = domain->iommu_did[iommu->seq_id];
 	int translation = CONTEXT_TT_MULTI_LEVEL;
-	struct device_domain_info *info = NULL;
 	struct context_entry *context;
-	unsigned long flags;
 	int ret;
 
 	WARN_ON(did == 0);
@@ -1925,7 +1918,6 @@ static int domain_context_mapping_one(struct dmar_domain *domain,
 
 	BUG_ON(!domain->pgd);
 
-	spin_lock_irqsave(&device_domain_lock, flags);
 	spin_lock(&iommu->lock);
 
 	ret = -ENOMEM;
@@ -1978,7 +1970,6 @@ static int domain_context_mapping_one(struct dmar_domain *domain,
 		 * Setup the Device-TLB enable bit and Page request
 		 * Enable bit:
 		 */
-		info = iommu_support_dev_iotlb(domain, iommu, bus, devfn);
 		if (info && info->ats_supported)
 			context_set_sm_dte(context);
 		if (info && info->pri_supported)
@@ -2001,7 +1992,6 @@ static int domain_context_mapping_one(struct dmar_domain *domain,
 					goto out_unlock;
 			}
 
-			info = iommu_support_dev_iotlb(domain, iommu, bus, devfn);
 			if (info && info->ats_supported)
 				translation = CONTEXT_TT_DEV_IOTLB;
 			else
@@ -2047,7 +2037,6 @@ static int domain_context_mapping_one(struct dmar_domain *domain,
 
 out_unlock:
 	spin_unlock(&iommu->lock);
-	spin_unlock_irqrestore(&device_domain_lock, flags);
 
 	return ret;
 }
@@ -2460,13 +2449,12 @@ static int domain_add_dev_info(struct dmar_domain *domain, struct device *dev)
 	if (!iommu)
 		return -ENODEV;
 
-	spin_lock_irqsave(&device_domain_lock, flags);
-	info->domain = domain;
 	ret = domain_attach_iommu(domain, iommu);
-	if (ret) {
-		spin_unlock_irqrestore(&device_domain_lock, flags);
+	if (ret)
 		return ret;
-	}
+
+	info->domain = domain;
+	spin_lock_irqsave(&device_domain_lock, flags);
 	list_add(&info->link, &domain->devices);
 	spin_unlock_irqrestore(&device_domain_lock, flags);
 
@@ -4636,7 +4624,6 @@ int intel_iommu_enable_pasid(struct intel_iommu *iommu, struct device *dev)
 	struct device_domain_info *info = dev_iommu_priv_get(dev);
 	struct context_entry *context;
 	struct dmar_domain *domain;
-	unsigned long flags;
 	u64 ctx_lo;
 	int ret;
 
@@ -4644,7 +4631,6 @@ int intel_iommu_enable_pasid(struct intel_iommu *iommu, struct device *dev)
 	if (!domain)
 		return -EINVAL;
 
-	spin_lock_irqsave(&device_domain_lock, flags);
 	spin_lock(&iommu->lock);
 
 	ret = -EINVAL;
@@ -4676,7 +4662,6 @@ int intel_iommu_enable_pasid(struct intel_iommu *iommu, struct device *dev)
 
  out:
 	spin_unlock(&iommu->lock);
-	spin_unlock_irqrestore(&device_domain_lock, flags);
 
 	return ret;
 }
-- 
2.25.1