diff --git a/hw/xen/xen-mapcache.c b/hw/xen/xen-mapcache.c
index 72a7e25e3e..4f98d284dd 100644
--- a/hw/xen/xen-mapcache.c
+++ b/hw/xen/xen-mapcache.c
@@ -23,13 +23,10 @@
 
 
 #if HOST_LONG_BITS == 32
-#  define MCACHE_BUCKET_SHIFT 16
 #  define MCACHE_MAX_SIZE     (1UL<<31) /* 2GB Cap */
 #else
-#  define MCACHE_BUCKET_SHIFT 20
 #  define MCACHE_MAX_SIZE     (1UL<<35) /* 32GB Cap */
 #endif
-#define MCACHE_BUCKET_SIZE (1UL << MCACHE_BUCKET_SHIFT)
 
 /* This is the size of the virtual address space reserve to QEMU that will not
  * be use by MapCache.
@@ -65,7 +62,8 @@ typedef struct MapCache {
     /* For most cases (>99.9%), the page address is the same. */
     MapCacheEntry *last_entry;
     unsigned long max_mcache_size;
-    unsigned int mcache_bucket_shift;
+    unsigned int bucket_shift;
+    unsigned long bucket_size;
 
     phys_offset_to_gaddr_t phys_offset_to_gaddr;
     QemuMutex lock;
@@ -95,6 +93,7 @@ static inline int test_bits(int nr, int size, const unsigned long *addr)
 
 static MapCache *xen_map_cache_init_single(phys_offset_to_gaddr_t f,
                                            void *opaque,
+                                           unsigned int bucket_shift,
                                            unsigned long max_size)
 {
     unsigned long size;
@@ -108,12 +107,14 @@ static MapCache *xen_map_cache_init_single(phys_offset_to_gaddr_t f,
 
     QTAILQ_INIT(&mc->locked_entries);
 
+    mc->bucket_shift = bucket_shift;
+    mc->bucket_size = 1UL << bucket_shift;
     mc->max_mcache_size = max_size;
 
     mc->nr_buckets =
         (((mc->max_mcache_size >> XC_PAGE_SHIFT) +
-          (1UL << (MCACHE_BUCKET_SHIFT - XC_PAGE_SHIFT)) - 1) >>
-         (MCACHE_BUCKET_SHIFT - XC_PAGE_SHIFT));
+          (1UL << (bucket_shift - XC_PAGE_SHIFT)) - 1) >>
+         (bucket_shift - XC_PAGE_SHIFT));
 
     size = mc->nr_buckets * sizeof(MapCacheEntry);
     size = (size + XC_PAGE_SIZE - 1) & ~(XC_PAGE_SIZE - 1);
@@ -126,6 +127,13 @@ void xen_map_cache_init(phys_offset_to_gaddr_t f, void *opaque)
 {
     struct rlimit rlimit_as;
     unsigned long max_mcache_size;
+    unsigned int bucket_shift;
+
+    if (HOST_LONG_BITS == 32) {
+        bucket_shift = 16;
+    } else {
+        bucket_shift = 20;
+    }
 
     if (geteuid() == 0) {
         rlimit_as.rlim_cur = RLIM_INFINITY;
@@ -146,7 +154,9 @@ void xen_map_cache_init(phys_offset_to_gaddr_t f, void *opaque)
         }
     }
 
-    mapcache = xen_map_cache_init_single(f, opaque, max_mcache_size);
+    mapcache = xen_map_cache_init_single(f, opaque,
+                                         bucket_shift,
+                                         max_mcache_size);
     setrlimit(RLIMIT_AS, &rlimit_as);
 }
 
@@ -195,7 +205,7 @@ static void xen_remap_bucket(MapCache *mc,
     entry->valid_mapping = NULL;
 
     for (i = 0; i < nb_pfn; i++) {
-        pfns[i] = (address_index << (MCACHE_BUCKET_SHIFT-XC_PAGE_SHIFT)) + i;
+        pfns[i] = (address_index << (mc->bucket_shift - XC_PAGE_SHIFT)) + i;
     }
 
     /*
@@ -266,8 +276,8 @@ static uint8_t *xen_map_cache_unlocked(MapCache *mc,
     bool dummy = false;
 
 tryagain:
-    address_index  = phys_addr >> MCACHE_BUCKET_SHIFT;
-    address_offset = phys_addr & (MCACHE_BUCKET_SIZE - 1);
+    address_index  = phys_addr >> mc->bucket_shift;
+    address_offset = phys_addr & (mc->bucket_size - 1);
 
     trace_xen_map_cache(phys_addr);
 
@@ -294,14 +304,14 @@ tryagain:
         return mc->last_entry->vaddr_base + address_offset;
     }
 
-    /* size is always a multiple of MCACHE_BUCKET_SIZE */
+    /* size is always a multiple of mc->bucket_size */
     if (size) {
         cache_size = size + address_offset;
-        if (cache_size % MCACHE_BUCKET_SIZE) {
-            cache_size += MCACHE_BUCKET_SIZE - (cache_size % MCACHE_BUCKET_SIZE);
+        if (cache_size % mc->bucket_size) {
+            cache_size += mc->bucket_size - (cache_size % mc->bucket_size);
         }
     } else {
-        cache_size = MCACHE_BUCKET_SIZE;
+        cache_size = mc->bucket_size;
     }
 
     entry = &mc->entry[address_index % mc->nr_buckets];
@@ -419,7 +429,7 @@ static ram_addr_t xen_ram_addr_from_mapcache_single(MapCache *mc, void *ptr)
         trace_xen_ram_addr_from_mapcache_not_in_cache(ptr);
         raddr = RAM_ADDR_INVALID;
     } else {
-        raddr = (reventry->paddr_index << MCACHE_BUCKET_SHIFT) +
+        raddr = (reventry->paddr_index << mc->bucket_shift) +
              ((unsigned long) ptr - (unsigned long) entry->vaddr_base);
     }
     mapcache_unlock(mc);
@@ -582,8 +592,8 @@ static uint8_t *xen_replace_cache_entry_unlocked(MapCache *mc,
     hwaddr address_index, address_offset;
     hwaddr test_bit_size, cache_size = size;
 
-    address_index  = old_phys_addr >> MCACHE_BUCKET_SHIFT;
-    address_offset = old_phys_addr & (MCACHE_BUCKET_SIZE - 1);
+    address_index  = old_phys_addr >> mc->bucket_shift;
+    address_offset = old_phys_addr & (mc->bucket_size - 1);
 
     assert(size);
     /* test_bit_size is always a multiple of XC_PAGE_SIZE */
@@ -592,8 +602,8 @@ static uint8_t *xen_replace_cache_entry_unlocked(MapCache *mc,
         test_bit_size += XC_PAGE_SIZE - (test_bit_size % XC_PAGE_SIZE);
     }
     cache_size = size + address_offset;
-    if (cache_size % MCACHE_BUCKET_SIZE) {
-        cache_size += MCACHE_BUCKET_SIZE - (cache_size % MCACHE_BUCKET_SIZE);
+    if (cache_size % mc->bucket_size) {
+        cache_size += mc->bucket_size - (cache_size % mc->bucket_size);
     }
 
     entry = &mc->entry[address_index % mc->nr_buckets];
@@ -606,8 +616,8 @@ static uint8_t *xen_replace_cache_entry_unlocked(MapCache *mc,
         return NULL;
     }
 
-    address_index  = new_phys_addr >> MCACHE_BUCKET_SHIFT;
-    address_offset = new_phys_addr & (MCACHE_BUCKET_SIZE - 1);
+    address_index  = new_phys_addr >> mc->bucket_shift;
+    address_offset = new_phys_addr & (mc->bucket_size - 1);
 
     trace_xen_replace_cache_entry_dummy(old_phys_addr, new_phys_addr);
 
