diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 4c80151313..cec3de08d2 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -320,6 +320,25 @@ const MemoryRegionOps vfio_region_ops = {
  * Device state interfaces
  */
 
+typedef struct {
+    unsigned long *bitmap;
+    hwaddr size;
+    hwaddr pages;
+} VFIOBitmap;
+
+static int vfio_bitmap_alloc(VFIOBitmap *vbmap, hwaddr size)
+{
+    vbmap->pages = REAL_HOST_PAGE_ALIGN(size) / qemu_real_host_page_size();
+    vbmap->size = ROUND_UP(vbmap->pages, sizeof(__u64) * BITS_PER_BYTE) /
+                                         BITS_PER_BYTE;
+    vbmap->bitmap = g_try_malloc0(vbmap->size);
+    if (!vbmap->bitmap) {
+        return -ENOMEM;
+    }
+
+    return 0;
+}
+
 bool vfio_mig_active(void)
 {
     VFIOGroup *group;
@@ -468,9 +487,14 @@ static int vfio_dma_unmap_bitmap(VFIOContainer *container,
 {
     struct vfio_iommu_type1_dma_unmap *unmap;
     struct vfio_bitmap *bitmap;
-    uint64_t pages = REAL_HOST_PAGE_ALIGN(size) / qemu_real_host_page_size();
+    VFIOBitmap vbmap;
     int ret;
 
+    ret = vfio_bitmap_alloc(&vbmap, size);
+    if (ret) {
+        return ret;
+    }
+
     unmap = g_malloc0(sizeof(*unmap) + sizeof(*bitmap));
 
     unmap->argsz = sizeof(*unmap) + sizeof(*bitmap);
@@ -484,35 +508,28 @@ static int vfio_dma_unmap_bitmap(VFIOContainer *container,
      * qemu_real_host_page_size to mark those dirty. Hence set bitmap_pgsize
      * to qemu_real_host_page_size.
      */
-
     bitmap->pgsize = qemu_real_host_page_size();
-    bitmap->size = ROUND_UP(pages, sizeof(__u64) * BITS_PER_BYTE) /
-                   BITS_PER_BYTE;
+    bitmap->size = vbmap.size;
+    bitmap->data = (__u64 *)vbmap.bitmap;
 
-    if (bitmap->size > container->max_dirty_bitmap_size) {
-        error_report("UNMAP: Size of bitmap too big 0x%"PRIx64,
-                     (uint64_t)bitmap->size);
+    if (vbmap.size > container->max_dirty_bitmap_size) {
+        error_report("UNMAP: Size of bitmap too big 0x%"PRIx64, vbmap.size);
         ret = -E2BIG;
         goto unmap_exit;
     }
 
-    bitmap->data = g_try_malloc0(bitmap->size);
-    if (!bitmap->data) {
-        ret = -ENOMEM;
-        goto unmap_exit;
-    }
-
     ret = ioctl(container->fd, VFIO_IOMMU_UNMAP_DMA, unmap);
     if (!ret) {
-        cpu_physical_memory_set_dirty_lebitmap((unsigned long *)bitmap->data,
-                iotlb->translated_addr, pages);
+        cpu_physical_memory_set_dirty_lebitmap(vbmap.bitmap,
+                iotlb->translated_addr, vbmap.pages);
     } else {
         error_report("VFIO_UNMAP_DMA with DIRTY_BITMAP : %m");
     }
 
-    g_free(bitmap->data);
 unmap_exit:
     g_free(unmap);
+    g_free(vbmap.bitmap);
+
     return ret;
 }
 
@@ -1329,7 +1346,7 @@ static int vfio_get_dirty_bitmap(VFIOContainer *container, uint64_t iova,
 {
     struct vfio_iommu_type1_dirty_bitmap *dbitmap;
     struct vfio_iommu_type1_dirty_bitmap_get *range;
-    uint64_t pages;
+    VFIOBitmap vbmap;
     int ret;
 
     if (!container->dirty_pages_supported) {
@@ -1339,6 +1356,11 @@ static int vfio_get_dirty_bitmap(VFIOContainer *container, uint64_t iova,
         return 0;
     }
 
+    ret = vfio_bitmap_alloc(&vbmap, size);
+    if (ret) {
+        return ret;
+    }
+
     dbitmap = g_malloc0(sizeof(*dbitmap) + sizeof(*range));
 
     dbitmap->argsz = sizeof(*dbitmap) + sizeof(*range);
@@ -1353,15 +1375,8 @@ static int vfio_get_dirty_bitmap(VFIOContainer *container, uint64_t iova,
      * to qemu_real_host_page_size.
      */
     range->bitmap.pgsize = qemu_real_host_page_size();
-
-    pages = REAL_HOST_PAGE_ALIGN(range->size) / qemu_real_host_page_size();
-    range->bitmap.size = ROUND_UP(pages, sizeof(__u64) * BITS_PER_BYTE) /
-                                         BITS_PER_BYTE;
-    range->bitmap.data = g_try_malloc0(range->bitmap.size);
-    if (!range->bitmap.data) {
-        ret = -ENOMEM;
-        goto err_out;
-    }
+    range->bitmap.size = vbmap.size;
+    range->bitmap.data = (__u64 *)vbmap.bitmap;
 
     ret = ioctl(container->fd, VFIO_IOMMU_DIRTY_PAGES, dbitmap);
     if (ret) {
@@ -1372,14 +1387,14 @@ static int vfio_get_dirty_bitmap(VFIOContainer *container, uint64_t iova,
         goto err_out;
     }
 
-    cpu_physical_memory_set_dirty_lebitmap((unsigned long *)range->bitmap.data,
-                                            ram_addr, pages);
+    cpu_physical_memory_set_dirty_lebitmap(vbmap.bitmap, ram_addr,
+                                           vbmap.pages);
 
     trace_vfio_get_dirty_bitmap(container->fd, range->iova, range->size,
                                 range->bitmap.size, ram_addr);
 err_out:
-    g_free(range->bitmap.data);
     g_free(dbitmap);
+    g_free(vbmap.bitmap);
 
     return ret;
 }