[Xen-devel] [PATCH v6 15/21] tools/libxc: Modify bitmap operations to take void pointers

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

The type of the pointer to a bitmap is not interesting; it does not affect the
representation of the block of bits being pointed to.

Make the libxc functions consistent with those in Xen, so they can work just
as well with 'unsigned int *' based bitmaps.

As part of doing so, change the implementation to be in terms of char rather
than unsigned long.  This fixes alignment concerns with ARM.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
CC: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
CC: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
CC: Julien Grall <julien.grall@xxxxxxx>

v2:
 * New
v3:
 * Implement in terms of char rather than unsigned long to fix alignment
   issues for ARM.
v4:
 * Fix erronious calculation in bitmap_size()
---
 tools/libxc/xc_bitops.h | 37 ++++++++++++++++++++-----------------
 tools/libxc/xc_misc.c   |  3 +++
 2 files changed, 23 insertions(+), 17 deletions(-)

diff --git a/tools/libxc/xc_bitops.h b/tools/libxc/xc_bitops.h
index cd749f4..3e7a544 100644
--- a/tools/libxc/xc_bitops.h
+++ b/tools/libxc/xc_bitops.h
@@ -6,70 +6,73 @@
 #include <stdlib.h>
 #include <string.h>
 
+/* Needed by several includees, but no longer used for bitops. */
 #define BITS_PER_LONG (sizeof(unsigned long) * 8)
 #define ORDER_LONG (sizeof(unsigned long) == 4 ? 5 : 6)
 
-#define BITMAP_ENTRY(_nr,_bmap) ((_bmap))[(_nr)/BITS_PER_LONG]
-#define BITMAP_SHIFT(_nr) ((_nr) % BITS_PER_LONG)
+#define BITMAP_ENTRY(_nr,_bmap) ((_bmap))[(_nr) / 8]
+#define BITMAP_SHIFT(_nr) ((_nr) % 8)
 
 /* calculate required space for number of longs needed to hold nr_bits */
 static inline int bitmap_size(int nr_bits)
 {
-    int nr_long, nr_bytes;
-    nr_long = (nr_bits + BITS_PER_LONG - 1) >> ORDER_LONG;
-    nr_bytes = nr_long * sizeof(unsigned long);
-    return nr_bytes;
+    return (nr_bits + 7) / 8;
 }
 
-static inline unsigned long *bitmap_alloc(int nr_bits)
+static inline void *bitmap_alloc(int nr_bits)
 {
     return calloc(1, bitmap_size(nr_bits));
 }
 
-static inline void bitmap_set(unsigned long *addr, int nr_bits)
+static inline void bitmap_set(void *addr, int nr_bits)
 {
     memset(addr, 0xff, bitmap_size(nr_bits));
 }
 
-static inline void bitmap_clear(unsigned long *addr, int nr_bits)
+static inline void bitmap_clear(void *addr, int nr_bits)
 {
     memset(addr, 0, bitmap_size(nr_bits));
 }
 
-static inline int test_bit(int nr, unsigned long *addr)
+static inline int test_bit(int nr, const void *_addr)
 {
+    const char *addr = _addr;
     return (BITMAP_ENTRY(nr, addr) >> BITMAP_SHIFT(nr)) & 1;
 }
 
-static inline void clear_bit(int nr, unsigned long *addr)
+static inline void clear_bit(int nr, void *_addr)
 {
+    char *addr = _addr;
     BITMAP_ENTRY(nr, addr) &= ~(1UL << BITMAP_SHIFT(nr));
 }
 
-static inline void set_bit(int nr, unsigned long *addr)
+static inline void set_bit(int nr, void *_addr)
 {
+    char *addr = _addr;
     BITMAP_ENTRY(nr, addr) |= (1UL << BITMAP_SHIFT(nr));
 }
 
-static inline int test_and_clear_bit(int nr, unsigned long *addr)
+static inline int test_and_clear_bit(int nr, void *addr)
 {
     int oldbit = test_bit(nr, addr);
     clear_bit(nr, addr);
     return oldbit;
 }
 
-static inline int test_and_set_bit(int nr, unsigned long *addr)
+static inline int test_and_set_bit(int nr, void *addr)
 {
     int oldbit = test_bit(nr, addr);
     set_bit(nr, addr);
     return oldbit;
 }
 
-static inline void bitmap_or(unsigned long *dst, const unsigned long *other,
+static inline void bitmap_or(void *_dst, const void *_other,
                              int nr_bits)
 {
-    int i, nr_longs = (bitmap_size(nr_bits) / sizeof(unsigned long));
-    for ( i = 0; i < nr_longs; ++i )
+    char *dst = _dst;
+    const char *other = _other;
+    int i;
+    for ( i = 0; i < bitmap_size(nr_bits); ++i )
         dst[i] |= other[i];
 }
 
diff --git a/tools/libxc/xc_misc.c b/tools/libxc/xc_misc.c
index 124537b..7d997d9 100644
--- a/tools/libxc/xc_misc.c
+++ b/tools/libxc/xc_misc.c
@@ -99,6 +99,9 @@ xc_cpumap_t xc_cpumap_alloc(xc_interface *xch)
  * byte aligned and so we need byte versions for architectures which do
  * not support misaligned accesses (which is basically everyone
  * but x86, although even on x86 it can be inefficient).
+ *
+ * NOTE: The xc_bitops macros now use byte alignment.
+ * TODO: Clean up the users of this interface.
  */
 #define BITS_PER_CPUMAP(map) (sizeof(*map) * 8)
 #define CPUMAP_ENTRY(cpu, map) ((map))[(cpu) / BITS_PER_CPUMAP(map)]
-- 
2.1.4


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