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>

1 files changed, 13 insertions, 11 deletions

diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
index 2c1b2babfdc5..dcf0295a9b60 100644
--- 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;