intel-iommu: Kill superfluous mapping_lock

Since we're using cmpxchg64() anyway (because that's the only way to do
an atomic 64-bit store on i386), we might as well ditch the extra
locking and just use cmpxchg64() to ensure that we don't add the page
twice.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

1 files changed, 2 insertions, 10 deletions

diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
index eea1006c860a..02223e2e27d4 100644
--- a/drivers/pci/intel-iommu.c
+++ b/drivers/pci/intel-iommu.c
@@ -267,7 +267,6 @@ struct dmar_domain {
         struct iova_domain iovad;       /* iova's that belong to this domain */
 
         struct dma_pte  *pgd;           /* virtual address */
-        spinlock_t      mapping_lock;   /* page table lock */
         int             gaw;            /* max guest address width */
 
         /* adjusted guest address width, 0 is level 2 30-bit */
@@ -701,13 +700,11 @@ static struct dma_pte *pfn_to_dma_pte(struct dmar_domain *domain,
         struct dma_pte *parent, *pte = NULL;
         int level = agaw_to_level(domain->agaw);
         int offset;
-        unsigned long flags;
 
         BUG_ON(!domain->pgd);
         BUG_ON(addr_width < BITS_PER_LONG && pfn >> addr_width);
         parent = domain->pgd;
 
-        spin_lock_irqsave(&domain->mapping_lock, flags);
         while (level > 0) {
                 void *tmp_page;
 
@@ -721,11 +718,9 @@ static struct dma_pte *pfn_to_dma_pte(struct dmar_domain *domain,
 
                         tmp_page = alloc_pgtable_page();
 
-                        if (!tmp_page) {
-                                spin_unlock_irqrestore(&domain->mapping_lock,
-                                        flags);
+                        if (!tmp_page)
                                 return NULL;
-                        }
+
                         domain_flush_cache(domain, tmp_page, VTD_PAGE_SIZE);
                         pteval = (virt_to_dma_pfn(tmp_page) << VTD_PAGE_SHIFT) | DMA_PTE_READ | DMA_PTE_WRITE;
                         if (cmpxchg64(&pte->val, 0ULL, pteval)) {
@@ -740,7 +735,6 @@ static struct dma_pte *pfn_to_dma_pte(struct dmar_domain *domain,
                 level--;
         }
 
-        spin_unlock_irqrestore(&domain->mapping_lock, flags);
         return pte;
 }
 
@@ -1375,7 +1369,6 @@ static int domain_init(struct dmar_domain *domain, int guest_width)
         unsigned long sagaw;
 
         init_iova_domain(&domain->iovad, DMA_32BIT_PFN);
-        spin_lock_init(&domain->mapping_lock);
         spin_lock_init(&domain->iommu_lock);
 
         domain_reserve_special_ranges(domain);
@@ -3336,7 +3329,6 @@ static int md_domain_init(struct dmar_domain *domain, int guest_width)
         int adjust_width;
 
         init_iova_domain(&domain->iovad, DMA_32BIT_PFN);
-        spin_lock_init(&domain->mapping_lock);
         spin_lock_init(&domain->iommu_lock);
 
         domain_reserve_special_ranges(domain);