[PATCH v2 8/8] iommu/arm-smmu-v3: Remove io-pgtable spinlock

Robin Murphy
2017-06-22T15:53:57Z

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.murphy-5wv7dgnIgG8@public.gmane.org>
---

v2: No change

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