linux-kernel - [PATCH v2 06/12] iommu/vt-d: Acquiring lock in domain ID allocation helpers

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Message-Id: <20220614025137.1632762-7-baolu.lu@linux.intel.com>
Date:   Tue, 14 Jun 2022 10:51:31 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Joerg Roedel <joro@...tes.org>, Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        Jason Gunthorpe <jgg@...dia.com>
Cc:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Liu Yi L <yi.l.liu@...el.com>,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Lu Baolu <baolu.lu@...ux.intel.com>
Subject: [PATCH v2 06/12] iommu/vt-d: Acquiring lock in domain ID allocation helpers

The iommu->lock is used to protect the per-IOMMU domain ID resource.
Moving the lock into the ID alloc/free helpers makes the code more
compact. At the same time, the device_domain_lock is irrelevant to
the domain ID resource, remove its assertion as well.

On the other hand, the iommu->lock is never used in interrupt context,
there's no need to use the irqsave variant of the spinlock calls.

Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
---
 drivers/iommu/intel/iommu.c | 25 +++++++++----------------
 1 file changed, 9 insertions(+), 16 deletions(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index b2ef8af0c3f3..8fdaa01ef10d 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -1782,16 +1782,13 @@ static struct dmar_domain *alloc_domain(unsigned int type)
 	return domain;
 }
 
-/* Must be called with iommu->lock */
 static int domain_attach_iommu(struct dmar_domain *domain,
 			       struct intel_iommu *iommu)
 {
 	unsigned long ndomains;
-	int num;
-
-	assert_spin_locked(&device_domain_lock);
-	assert_spin_locked(&iommu->lock);
+	int num, ret = 0;
 
+	spin_lock(&iommu->lock);
 	domain->iommu_refcnt[iommu->seq_id] += 1;
 	if (domain->iommu_refcnt[iommu->seq_id] == 1) {
 		ndomains = cap_ndoms(iommu->cap);
@@ -1800,7 +1797,8 @@ static int domain_attach_iommu(struct dmar_domain *domain,
 		if (num >= ndomains) {
 			pr_err("%s: No free domain ids\n", iommu->name);
 			domain->iommu_refcnt[iommu->seq_id] -= 1;
-			return -ENOSPC;
+			ret = -ENOSPC;
+			goto out_unlock;
 		}
 
 		set_bit(num, iommu->domain_ids);
@@ -1809,7 +1807,9 @@ static int domain_attach_iommu(struct dmar_domain *domain,
 		domain_update_iommu_cap(domain);
 	}
 
-	return 0;
+out_unlock:
+	spin_unlock(&iommu->lock);
+	return ret;
 }
 
 static void domain_detach_iommu(struct dmar_domain *domain,
@@ -1817,9 +1817,7 @@ static void domain_detach_iommu(struct dmar_domain *domain,
 {
 	int num;
 
-	assert_spin_locked(&device_domain_lock);
-	assert_spin_locked(&iommu->lock);
-
+	spin_lock(&iommu->lock);
 	domain->iommu_refcnt[iommu->seq_id] -= 1;
 	if (domain->iommu_refcnt[iommu->seq_id] == 0) {
 		num = domain->iommu_did[iommu->seq_id];
@@ -1827,6 +1825,7 @@ static void domain_detach_iommu(struct dmar_domain *domain,
 		domain_update_iommu_cap(domain);
 		domain->iommu_did[iommu->seq_id] = 0;
 	}
+	spin_unlock(&iommu->lock);
 }
 
 static inline int guestwidth_to_adjustwidth(int gaw)
@@ -2479,9 +2478,7 @@ static int domain_add_dev_info(struct dmar_domain *domain, struct device *dev)
 
 	spin_lock_irqsave(&device_domain_lock, flags);
 	info->domain = domain;
-	spin_lock(&iommu->lock);
 	ret = domain_attach_iommu(domain, iommu);
-	spin_unlock(&iommu->lock);
 	if (ret) {
 		spin_unlock_irqrestore(&device_domain_lock, flags);
 		return ret;
@@ -4166,7 +4163,6 @@ static void __dmar_remove_one_dev_info(struct device_domain_info *info)
 {
 	struct dmar_domain *domain;
 	struct intel_iommu *iommu;
-	unsigned long flags;
 
 	assert_spin_locked(&device_domain_lock);
 
@@ -4187,10 +4183,7 @@ static void __dmar_remove_one_dev_info(struct device_domain_info *info)
 	}
 
 	list_del(&info->link);
-
-	spin_lock_irqsave(&iommu->lock, flags);
 	domain_detach_iommu(domain, iommu);
-	spin_unlock_irqrestore(&iommu->lock, flags);
 }
 
 static void dmar_remove_one_dev_info(struct device *dev)
-- 
2.25.1