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Subject[PATCH 10/10] iommu/amd: make amd_iommu_devtable_lock a spin_lock
Date
Before commit 0bb6e243d7fb ("iommu/amd: Support IOMMU_DOMAIN_DMA type
allocation") amd_iommu_devtable_lock had a read_lock() user but now
there are none. In fact, after the mentioned commit we had only
write_lock() user of the lock. Since there is no reason to keep it as
writer lock, change its type to a spin_lock.
I *think* that we might even be able to remove the lock because all its
current user seem to have their own protection.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
drivers/iommu/amd_iommu.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 0a7ca5e95288..6ed59f1f6d33 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -80,7 +80,7 @@
*/
#define AMD_IOMMU_PGSIZES ((~0xFFFUL) & ~(2ULL << 38))

-static DEFINE_RWLOCK(amd_iommu_devtable_lock);
+static DEFINE_SPINLOCK(amd_iommu_devtable_lock);
static DEFINE_SPINLOCK(pd_bitmap_lock);
static DEFINE_RAW_SPINLOCK(iommu_table_lock);

@@ -2097,9 +2097,9 @@ static int attach_device(struct device *dev,
}

skip_ats_check:
- write_lock_irqsave(&amd_iommu_devtable_lock, flags);
+ spin_lock_irqsave(&amd_iommu_devtable_lock, flags);
ret = __attach_device(dev_data, domain);
- write_unlock_irqrestore(&amd_iommu_devtable_lock, flags);
+ spin_unlock_irqrestore(&amd_iommu_devtable_lock, flags);

/*
* We might boot into a crash-kernel here. The crashed kernel
@@ -2149,9 +2149,9 @@ static void detach_device(struct device *dev)
domain = dev_data->domain;

/* lock device table */
- write_lock_irqsave(&amd_iommu_devtable_lock, flags);
+ spin_lock_irqsave(&amd_iommu_devtable_lock, flags);
__detach_device(dev_data);
- write_unlock_irqrestore(&amd_iommu_devtable_lock, flags);
+ spin_unlock_irqrestore(&amd_iommu_devtable_lock, flags);

if (!dev_is_pci(dev))
return;
@@ -2814,7 +2814,7 @@ static void cleanup_domain(struct protection_domain *domain)
struct iommu_dev_data *entry;
unsigned long flags;

- write_lock_irqsave(&amd_iommu_devtable_lock, flags);
+ spin_lock_irqsave(&amd_iommu_devtable_lock, flags);

while (!list_empty(&domain->dev_list)) {
entry = list_first_entry(&domain->dev_list,
@@ -2822,7 +2822,7 @@ static void cleanup_domain(struct protection_domain *domain)
__detach_device(entry);
}

- write_unlock_irqrestore(&amd_iommu_devtable_lock, flags);
+ spin_unlock_irqrestore(&amd_iommu_devtable_lock, flags);
}

static void protection_domain_free(struct protection_domain *domain)
--
2.16.2
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