[PATCH v4 04/11] iommu/vt-d: Unnecessary spinlock for root table alloc and free

Lu Baolu
2022-07-06T03:00:17Z

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.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@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