[PATCH] xen: simplify bitmap_to_xenctl_bitmap for little endian

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

The little endian implementation of bitmap_to_xenctl_bitmap leads to
unnecessary xmallocs and xfrees. Given that Xen only supports little
endian architectures, it is worth optimizing.

This patch removes the need for the xmalloc on little endian
architectures.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxx>

diff --git a/xen/common/bitmap.c b/xen/common/bitmap.c
index 3da63a32a6..38d77fc876 100644
--- a/xen/common/bitmap.c
+++ b/xen/common/bitmap.c
@@ -384,21 +384,26 @@ int bitmap_to_xenctl_bitmap(struct xenctl_bitmap 
*xenctl_bitmap,
     uint8_t zero = 0;
     int err = 0;
     unsigned int xen_bytes = DIV_ROUND_UP(nbits, BITS_PER_BYTE);
-    uint8_t *bytemap = xmalloc_array(uint8_t, xen_bytes);
-
-    if ( !bytemap )
-        return -ENOMEM;
+    uint8_t *bytemap = (uint8_t *)bitmap;
 
     guest_bytes = DIV_ROUND_UP(xenctl_bitmap->nr_bits, BITS_PER_BYTE);
     copy_bytes  = min(guest_bytes, xen_bytes);
 
-    bitmap_long_to_byte(bytemap, bitmap, nbits);
+    if ( IS_ENABLED(__BIG_ENDIAN) )
+    {
+        bytemap = xmalloc_array(uint8_t, xen_bytes);
+        if ( !bytemap )
+            return -ENOMEM;
+
+        bitmap_long_to_byte(bytemap, bitmap, nbits);
+    }
 
     if ( copy_bytes &&
          copy_to_guest(xenctl_bitmap->bitmap, bytemap, copy_bytes) )
         err = -EFAULT;
 
-    xfree(bytemap);
+    if ( IS_ENABLED(__BIG_ENDIAN) )
+        xfree(bytemap);
 
     for ( i = copy_bytes; !err && i < guest_bytes; i++ )
         if ( copy_to_guest_offset(xenctl_bitmap->bitmap, i, &zero, 1) )