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>

diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
index eea1006c860a18300c5a511e61a8ce2f8cc70e17..02223e2e27d4380e34ed49b17484ac7374e30a8e 100644 (file)
--- 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);