[Xen-devel] [PATCH v2 16/18] mini-os: map page allocator's bitmap to virtual kernel area for ballooning

[Juergen Gross <jgross@xxxxxxxx>]

In case of CONFIG_BALLOON the page allocator's bitmap needs some space
to be able to grow. Remap it to kernel virtual area if the preallocated
area isn't large enough.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 balloon.c         | 17 +++++++++++++++++
 include/balloon.h |  2 ++
 include/mm.h      |  6 ++++++
 mm.c              | 19 ++++++++++---------
 4 files changed, 35 insertions(+), 9 deletions(-)

diff --git a/balloon.c b/balloon.c
index 4c18c5c..75b87c8 100644
--- a/balloon.c
+++ b/balloon.c
@@ -44,3 +44,20 @@ void get_max_pages(void)
     nr_max_pages = ret;
     printk("Maximum memory size: %ld pages\n", nr_max_pages);
 }
+
+void alloc_bitmap_remap(void)
+{
+    unsigned long i;
+
+    if ( alloc_bitmap_size >= ((nr_max_pages + 1) >> (PAGE_SHIFT + 3)) )
+        return;
+
+    for ( i = 0; i < alloc_bitmap_size; i += PAGE_SIZE )
+    {
+        map_frame_rw(virt_kernel_area_end + i,
+                     virt_to_mfn((unsigned long)(alloc_bitmap) + i));
+    }
+
+    alloc_bitmap = (unsigned long *)virt_kernel_area_end;
+    virt_kernel_area_end += round_pgup((nr_max_pages + 1) >> (PAGE_SHIFT + 3));
+}
diff --git a/include/balloon.h b/include/balloon.h
index b8d9335..0e2340b 100644
--- a/include/balloon.h
+++ b/include/balloon.h
@@ -31,11 +31,13 @@ extern unsigned long virt_kernel_area_end;
 
 void get_max_pages(void);
 void arch_remap_p2m(unsigned long max_pfn);
+void alloc_bitmap_remap(void);
 
 #else /* CONFIG_BALLOON */
 
 static inline void get_max_pages(void) { }
 static inline void arch_remap_p2m(unsigned long max_pfn) { }
+static inline void alloc_bitmap_remap(void) { }
 
 #endif /* CONFIG_BALLOON */
 #endif /* _BALLOON_H_ */
diff --git a/include/mm.h b/include/mm.h
index 6add683..73c59c4 100644
--- a/include/mm.h
+++ b/include/mm.h
@@ -42,8 +42,14 @@
 #define STACK_SIZE_PAGE_ORDER __STACK_SIZE_PAGE_ORDER
 #define STACK_SIZE __STACK_SIZE
 
+#define round_pgdown(_p)  ((_p) & PAGE_MASK)
+#define round_pgup(_p)    (((_p) + (PAGE_SIZE - 1)) & PAGE_MASK)
+
 extern unsigned long nr_free_pages;
 
+extern unsigned long *alloc_bitmap;
+extern unsigned long alloc_bitmap_size;
+
 void init_mm(void);
 unsigned long alloc_pages(int order);
 #define alloc_page()    alloc_pages(0)
diff --git a/mm.c b/mm.c
index fd66115..13bb3e5 100644
--- a/mm.c
+++ b/mm.c
@@ -48,7 +48,9 @@
  *  One bit per page of memory. Bit set => page is allocated.
  */
 
-static unsigned long *alloc_bitmap;
+unsigned long *alloc_bitmap;
+unsigned long alloc_bitmap_size;
+
 #define PAGES_PER_MAPWORD (sizeof(unsigned long) * 8)
 
 #define allocated_in_map(_pn) \
@@ -137,9 +139,6 @@ static chunk_head_t *free_head[FREELIST_SIZE];
 static chunk_head_t  free_tail[FREELIST_SIZE];
 #define FREELIST_EMPTY(_l) ((_l)->next == NULL)
 
-#define round_pgdown(_p)  ((_p)&PAGE_MASK)
-#define round_pgup(_p)    (((_p)+(PAGE_SIZE-1))&PAGE_MASK)
-
 /*
  * Initialise allocator, placing addresses [@min,@max] in free pool.
  * @min and @max are PHYSICAL addresses.
@@ -147,7 +146,7 @@ static chunk_head_t  free_tail[FREELIST_SIZE];
 static void init_page_allocator(unsigned long min, unsigned long max)
 {
     int i;
-    unsigned long range, bitmap_size;
+    unsigned long range;
     chunk_head_t *ch;
     chunk_tail_t *ct;
     for ( i = 0; i < FREELIST_SIZE; i++ )
@@ -161,14 +160,14 @@ static void init_page_allocator(unsigned long min, 
unsigned long max)
     max = round_pgdown(max);
 
     /* Allocate space for the allocation bitmap. */
-    bitmap_size  = (max+1) >> (PAGE_SHIFT+3);
-    bitmap_size  = round_pgup(bitmap_size);
+    alloc_bitmap_size  = (max + 1) >> (PAGE_SHIFT + 3);
+    alloc_bitmap_size  = round_pgup(alloc_bitmap_size);
     alloc_bitmap = (unsigned long *)to_virt(min);
-    min         += bitmap_size;
+    min         += alloc_bitmap_size;
     range        = max - min;
 
     /* All allocated by default. */
-    memset(alloc_bitmap, ~0, bitmap_size);
+    memset(alloc_bitmap, ~0, alloc_bitmap_size);
     /* Free up the memory we've been given to play with. */
     map_free(PHYS_PFN(min), range>>PAGE_SHIFT);
 
@@ -198,6 +197,8 @@ static void init_page_allocator(unsigned long min, unsigned 
long max)
         free_head[i]    = ch;
         ct->level       = i;
     }
+
+    alloc_bitmap_remap();
 }
 
 
-- 
2.6.6


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