[PATCH 04/16] arm: handle xenheap which isn't at the start of RAM.

[Ian Campbell <ian.campbell@citrix.com>]

Also refactor page_to_virt somewhat in an attempt to make it clearer
what is happening.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
---
 xen/include/asm-arm/mm.h |   24 +++++++++++++++++++-----
 1 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/xen/include/asm-arm/mm.h b/xen/include/asm-arm/mm.h
index b37bd35..6498322 100644
--- a/xen/include/asm-arm/mm.h
+++ b/xen/include/asm-arm/mm.h
@@ -214,17 +214,31 @@ static inline struct page_info *virt_to_page(const void *v)
     ASSERT(va >= XENHEAP_VIRT_START);
     ASSERT(va < xenheap_virt_end);
 
-    return frame_table + ((va - XENHEAP_VIRT_START) >> PAGE_SHIFT);
+    return frame_table
+        + ((va - XENHEAP_VIRT_START) >> PAGE_SHIFT)
+        + xenheap_mfn_start
+        - frametable_base_mfn;
 }
 
 static inline void *page_to_virt(const struct page_info *pg)
 {
+    unsigned long va;
+    const unsigned long offset =
+        (xenheap_mfn_start-frametable_base_mfn)*sizeof(*pg);
+
+    /*
+     * Dividing by this on both top and bottom factors out the largest
+     * common factor of 2 which helps the compiler to use smaller shifts.
+     */
+    const unsigned long lcd = (sizeof(*pg) & -sizeof(*pg));
+
     ASSERT((unsigned long)pg - FRAMETABLE_VIRT_START < frametable_virt_end);
-    return (void *)(XENHEAP_VIRT_START +
-                    ((unsigned long)pg - FRAMETABLE_VIRT_START) /
-                    (sizeof(*pg) / (sizeof(*pg) & -sizeof(*pg))) *
-                    (PAGE_SIZE / (sizeof(*pg) & -sizeof(*pg))));
 
+    va = (unsigned long)pg;
+    va = XENHEAP_VIRT_START +
+        ((va - FRAMETABLE_VIRT_START - offset) / (sizeof(*pg) / lcd)) *
+        (PAGE_SIZE / lcd);
+    return (void *)va;
 }
 
 struct domain *page_get_owner_and_reference(struct page_info *page);
-- 
1.7.9.1