[PATCH v3 06/13] vm/page: provide PGDIR_OFFSET() macro

[Peter Xu <peterx@xxxxxxxxxx>]

This can be used in further patches.

Reviewed-by: Andrew Jones <drjones@xxxxxxxxxx>
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
---
 lib/x86/asm/page.h | 3 +++
 lib/x86/vm.c       | 4 ++--
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/lib/x86/asm/page.h b/lib/x86/asm/page.h
index 5044a49..c43bab2 100644
--- a/lib/x86/asm/page.h
+++ b/lib/x86/asm/page.h
@@ -41,5 +41,8 @@
 #define	PGDIR_MASK	1023
 #endif
 
+#define PGDIR_BITS(lvl)        (((lvl) - 1) * PGDIR_WIDTH + PAGE_SHIFT)
+#define PGDIR_OFFSET(va, lvl)  (((va) >> PGDIR_BITS(lvl)) & PGDIR_MASK)
+
 #endif /* !__ASSEMBLY__ */
 #endif
diff --git a/lib/x86/vm.c b/lib/x86/vm.c
index f7e778b..cda4c5f 100644
--- a/lib/x86/vm.c
+++ b/lib/x86/vm.c
@@ -48,7 +48,7 @@ unsigned long *install_pte(unsigned long *cr3,
     unsigned offset;
 
     for (level = PAGE_LEVEL; level > pte_level; --level) {
-	offset = ((unsigned long)virt >> ((level-1) * PGDIR_WIDTH + 12)) & PGDIR_MASK;
+	offset = PGDIR_OFFSET((unsigned long)virt, level);
 	if (!(pt[offset] & PT_PRESENT_MASK)) {
 	    unsigned long *new_pt = pt_page;
             if (!new_pt)
@@ -60,7 +60,7 @@ unsigned long *install_pte(unsigned long *cr3,
 	}
 	pt = phys_to_virt(pt[offset] & PT_ADDR_MASK);
     }
-    offset = ((unsigned long)virt >> ((level-1) * PGDIR_WIDTH + 12)) & PGDIR_MASK;
+    offset = PGDIR_OFFSET((unsigned long)virt, level);
     pt[offset] = pte;
     return &pt[offset];
 }
-- 
2.7.4

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