diff --git a/xen/common/bitmap.c b/xen/common/bitmap.c
index 3da63a32a6..6c4af09c18 100644
--- a/xen/common/bitmap.c
+++ b/xen/common/bitmap.c
@@ -40,21 +40,6 @@
  * for the best explanations of this ordering.
  */
 
-/*
- * If a bitmap has a number of bits which is not a multiple of 8 then
- * the last few bits of the last byte of the bitmap can be
- * unexpectedly set which can confuse consumers (e.g. in the tools)
- * who also round up their loops to 8 bits. Ensure we clear those left
- * over bits so as to prevent surprises.
- */
-static void clamp_last_byte(uint8_t *bp, unsigned int nbits)
-{
-	unsigned int remainder = nbits % 8;
-
-	if (remainder)
-		bp[nbits/8] &= (1U << remainder) - 1;
-}
-
 int __bitmap_empty(const unsigned long *bitmap, unsigned int bits)
 {
 	int k, lim = bits/BITS_PER_LONG;
@@ -338,7 +323,6 @@ static void bitmap_long_to_byte(uint8_t *bp, const unsigned long *lp,
 			nbits -= 8;
 		}
 	}
-	clamp_last_byte(bp, nbits);
 }
 
 static void bitmap_byte_to_long(unsigned long *lp, const uint8_t *bp,
@@ -359,12 +343,11 @@ static void bitmap_byte_to_long(unsigned long *lp, const uint8_t *bp,
 
 #elif defined(__LITTLE_ENDIAN)
 
-static void bitmap_long_to_byte(uint8_t *bp, const unsigned long *lp,
-				unsigned int nbits)
-{
-	memcpy(bp, lp, DIV_ROUND_UP(nbits, BITS_PER_BYTE));
-	clamp_last_byte(bp, nbits);
-}
+#define LITTLE_ENDIAN 1 /* For IS_ENABLED(). */
+
+/* Unused function, but a declaration is needed. */
+void bitmap_long_to_byte(uint8_t *bp, const unsigned long *lp,
+			 unsigned int nbits);
 
 static void bitmap_byte_to_long(unsigned long *lp, const uint8_t *bp,
 				unsigned int nbits)
@@ -384,21 +367,45 @@ 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);
+    const uint8_t *bytemap;
+    uint8_t last, *buf = NULL;
 
-    if ( !bytemap )
-        return -ENOMEM;
+    if ( !IS_ENABLED(LITTLE_ENDIAN) )
+    {
+        buf = xmalloc_array(uint8_t, xen_bytes);
+        if ( !buf )
+            return -ENOMEM;
+
+        bitmap_long_to_byte(buf, bitmap, nbits);
+
+        bytemap = buf;
+    }
+    else
+        bytemap = (const 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 ( copy_bytes &&
-         copy_to_guest(xenctl_bitmap->bitmap, bytemap, copy_bytes) )
+    if ( copy_bytes > 1 &&
+         copy_to_guest(xenctl_bitmap->bitmap, bytemap, copy_bytes - 1) )
         err = -EFAULT;
 
-    xfree(bytemap);
+    /*
+     * If a bitmap has a number of bits which is not a multiple of 8 then the
+     * last few bits of the last byte of the bitmap can be unexpectedly set,
+     * which can confuse consumers (e.g. in the tools), who also may round up
+     * their loops to 8 bits. Ensure we clear those left over bits so as to
+     * prevent surprises.
+     */
+    last = bytemap[nbits / 8];
+    if ( nbits % 8 )
+        last &= (1U << (nbits % 8)) - 1;
+
+    xfree(buf);
+
+    if ( copy_bytes &&
+         copy_to_guest_offset(xenctl_bitmap->bitmap, copy_bytes - 1, &last, 1) )
+        err = -EFAULT;
 
     for ( i = copy_bytes; !err && i < guest_bytes; i++ )
         if ( copy_to_guest_offset(xenctl_bitmap->bitmap, i, &zero, 1) )