[PATCH 8/8] iommu/arm-smmu-v3: Remove io-pgtable spinlock

[Robin Murphy]

As for SMMUv2, take advantage of io-pgtable's newfound tolerance for
concurrency. Unfortunately in this case the command queue lock remains a
point of serialisation for the unmap path, but there may be a little
more we can do to ameliorate that in future.

Signed-off-by: Robin Murphy <robin.mur...@arm.com>
---
 drivers/iommu/arm-smmu-v3.c | 33 ++++++---------------------------
 1 file changed, 6 insertions(+), 27 deletions(-)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index b9c4cf4ccca2..291da5f918d5 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -645,7 +645,6 @@ struct arm_smmu_domain {
        struct mutex                    init_mutex; /* Protects smmu pointer */
 
        struct io_pgtable_ops           *pgtbl_ops;
-       spinlock_t                      pgtbl_lock;
 
        enum arm_smmu_domain_stage      stage;
        union {
@@ -1406,7 +1405,6 @@ static struct iommu_domain 
*arm_smmu_domain_alloc(unsigned type)
        }
 
        mutex_init(&smmu_domain->init_mutex);
-       spin_lock_init(&smmu_domain->pgtbl_lock);
        return &smmu_domain->domain;
 }
 
@@ -1678,44 +1676,29 @@ static int arm_smmu_attach_dev(struct iommu_domain 
*domain, struct device *dev)
 static int arm_smmu_map(struct iommu_domain *domain, unsigned long iova,
                        phys_addr_t paddr, size_t size, int prot)
 {
-       int ret;
-       unsigned long flags;
-       struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
-       struct io_pgtable_ops *ops = smmu_domain->pgtbl_ops;
+       struct io_pgtable_ops *ops = to_smmu_domain(domain)->pgtbl_ops;
 
        if (!ops)
                return -ENODEV;
 
-       spin_lock_irqsave(&smmu_domain->pgtbl_lock, flags);
-       ret = ops->map(ops, iova, paddr, size, prot);
-       spin_unlock_irqrestore(&smmu_domain->pgtbl_lock, flags);
-       return ret;
+       return ops->map(ops, iova, paddr, size, prot);
 }
 
 static size_t
 arm_smmu_unmap(struct iommu_domain *domain, unsigned long iova, size_t size)
 {
-       size_t ret;
-       unsigned long flags;
-       struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
-       struct io_pgtable_ops *ops = smmu_domain->pgtbl_ops;
+       struct io_pgtable_ops *ops = to_smmu_domain(domain)->pgtbl_ops;
 
        if (!ops)
                return 0;
 
-       spin_lock_irqsave(&smmu_domain->pgtbl_lock, flags);
-       ret = ops->unmap(ops, iova, size);
-       spin_unlock_irqrestore(&smmu_domain->pgtbl_lock, flags);
-       return ret;
+       return ops->unmap(ops, iova, size);
 }
 
 static phys_addr_t
 arm_smmu_iova_to_phys(struct iommu_domain *domain, dma_addr_t iova)
 {
-       phys_addr_t ret;
-       unsigned long flags;
-       struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
-       struct io_pgtable_ops *ops = smmu_domain->pgtbl_ops;
+       struct io_pgtable_ops *ops = to_smmu_domain(domain)->pgtbl_ops;
 
        if (domain->type == IOMMU_DOMAIN_IDENTITY)
                return iova;
@@ -1723,11 +1706,7 @@ arm_smmu_iova_to_phys(struct iommu_domain *domain, 
dma_addr_t iova)
        if (!ops)
                return 0;
 
-       spin_lock_irqsave(&smmu_domain->pgtbl_lock, flags);
-       ret = ops->iova_to_phys(ops, iova);
-       spin_unlock_irqrestore(&smmu_domain->pgtbl_lock, flags);
-
-       return ret;
+       return ops->iova_to_phys(ops, iova);
 }
 
 static struct platform_driver arm_smmu_driver;
-- 
2.12.2.dirty

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