[PATCH v3 04/11] iommu/vt-d: Unnecessary spinlock for root table alloc and free

[Lu Baolu]

The IOMMU root table is allocated and freed in the IOMMU initialization
code in static boot or hot-remove paths. There's no need for a spinlock.

Signed-off-by: Lu Baolu <baolu...@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.t...@intel.com>
---
 drivers/iommu/intel/iommu.c | 18 +++++-------------
 1 file changed, 5 insertions(+), 13 deletions(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 77915d61f7ec..ff49c9460ede 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -809,14 +809,12 @@ static int device_context_mapped(struct intel_iommu 
*iommu, u8 bus, u8 devfn)
 
 static void free_context_table(struct intel_iommu *iommu)
 {
-       int i;
-       unsigned long flags;
        struct context_entry *context;
+       int i;
+
+       if (!iommu->root_entry)
+               return;
 
-       spin_lock_irqsave(&iommu->lock, flags);
-       if (!iommu->root_entry) {
-               goto out;
-       }
        for (i = 0; i < ROOT_ENTRY_NR; i++) {
                context = iommu_context_addr(iommu, i, 0, 0);
                if (context)
@@ -828,12 +826,10 @@ static void free_context_table(struct intel_iommu *iommu)
                context = iommu_context_addr(iommu, i, 0x80, 0);
                if (context)
                        free_pgtable_page(context);
-
        }
+
        free_pgtable_page(iommu->root_entry);
        iommu->root_entry = NULL;
-out:
-       spin_unlock_irqrestore(&iommu->lock, flags);
 }
 
 #ifdef CONFIG_DMAR_DEBUG
@@ -1232,7 +1228,6 @@ static void domain_unmap(struct dmar_domain *domain, 
unsigned long start_pfn,
 static int iommu_alloc_root_entry(struct intel_iommu *iommu)
 {
        struct root_entry *root;
-       unsigned long flags;
 
        root = (struct root_entry *)alloc_pgtable_page(iommu->node);
        if (!root) {
@@ -1242,10 +1237,7 @@ static int iommu_alloc_root_entry(struct intel_iommu 
*iommu)
        }
 
        __iommu_flush_cache(iommu, root, ROOT_SIZE);
-
-       spin_lock_irqsave(&iommu->lock, flags);
        iommu->root_entry = root;
-       spin_unlock_irqrestore(&iommu->lock, flags);
 
        return 0;
 }
-- 
2.25.1

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