From: Sebastian Andrzej Siewior Date: Thu, 22 Mar 2018 16:22:41 +0100 Subject: [PATCH 09/10] iommu/amd: Make amd_iommu_devtable_lock a spin_lock Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.16/older/patches-4.16.8-rt3.tar.xz Upstream commit 2cd1083d79a0a8c223af430ca97884c28a1e2fc0 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 Signed-off-by: Joerg Roedel --- drivers/iommu/amd_iommu.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) --- 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_SPINLOCK(iommu_table_lock); @@ -2096,9 +2096,9 @@ static int attach_device(struct device * } 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 @@ -2148,9 +2148,9 @@ static void detach_device(struct device 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; @@ -2813,7 +2813,7 @@ static void cleanup_domain(struct protec 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, @@ -2821,7 +2821,7 @@ static void cleanup_domain(struct protec __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)