intel-iommu: Introduce first_pte_in_page() to simplify PTE-setting loops

On Wed, 2009-07-01 at 16:59 -0700, Linus Torvalds wrote:
> I also _really_ hate how you do
>
>         (unsigned long)pte >> VTD_PAGE_SHIFT ==
>         (unsigned long)first_pte >> VTD_PAGE_SHIFT

Kill this, in favour of just looking to see if the incremented pte
pointer has 'wrapped' onto the next page. Which means we have to check
it _after_ incrementing it, not before.

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

diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
index 2c1b2ba..dcf0295 100644 (file)
--- a/drivers/pci/intel-iommu.c
+++ b/drivers/pci/intel-iommu.c
@@ -240,6 +240,11 @@ static inline bool dma_pte_present(struct dma_pte *pte)
        return (pte->val & 3) != 0;
 }
 
+static inline int first_pte_in_page(struct dma_pte *pte)
+{
+       return !((unsigned long)pte & ~VTD_PAGE_MASK);
+}
+
 /*
  * This domain is a statically identity mapping domain.
  *     1. This domain creats a static 1:1 mapping to all usable memory.
@@ -780,13 +785,12 @@ static void dma_pte_clear_range(struct dmar_domain *domain,
                        start_pfn = align_to_level(start_pfn + 1, 2);
                        continue;
                }
-               while (start_pfn <= last_pfn &&
-                      (unsigned long)pte >> VTD_PAGE_SHIFT ==
-                      (unsigned long)first_pte >> VTD_PAGE_SHIFT) {
+               do { 
                        dma_clear_pte(pte);
                        start_pfn++;
                        pte++;
-               }
+               } while (start_pfn <= last_pfn && !first_pte_in_page(pte));
+
                domain_flush_cache(domain, first_pte,
                                   (void *)pte - (void *)first_pte);
        }
@@ -821,14 +825,14 @@ static void dma_pte_free_pagetable(struct dmar_domain *domain,
                                tmp = align_to_level(tmp + 1, level + 1);
                                continue;
                        }
-                       while (tmp + level_size(level) - 1 <= last_pfn &&
-                              (unsigned long)pte >> VTD_PAGE_SHIFT ==
-                              (unsigned long)first_pte >> VTD_PAGE_SHIFT) {
+                       do {
                                free_pgtable_page(phys_to_virt(dma_pte_addr(pte)));
                                dma_clear_pte(pte);
                                pte++;
                                tmp += level_size(level);
-                       }
+                       } while (!first_pte_in_page(pte) &&
+                                tmp + level_size(level) - 1 <= last_pfn);
+
                        domain_flush_cache(domain, first_pte,
                                           (void *)pte - (void *)first_pte);
                        
@@ -1694,9 +1698,7 @@ static int __domain_mapping(struct dmar_domain *domain, unsigned long iov_pfn,
                        WARN_ON(1);
                }
                pte++;
-               if (!nr_pages ||
-                   (unsigned long)pte >> VTD_PAGE_SHIFT !=
-                   (unsigned long)first_pte >> VTD_PAGE_SHIFT) {
+               if (!nr_pages || first_pte_in_page(pte)) {
                        domain_flush_cache(domain, first_pte,
                                           (void *)pte - (void *)first_pte);
                        pte = NULL;