diff --git a/src/intel/vulkan/anv_device.c b/src/intel/vulkan/anv_device.c
index e082cdce09f..1252ad70cc7 100644
--- a/src/intel/vulkan/anv_device.c
+++ b/src/intel/vulkan/anv_device.c
@@ -1792,17 +1792,8 @@ VkResult anv_MapMemory2KHR(
       placed_addr = placed_info->pPlacedAddress;
    }
 
-   /* GEM will fail to map if the offset isn't 4k-aligned.  Round down. */
-   uint64_t map_offset;
-   if (!device->physical->info.has_mmap_offset)
-      map_offset = offset & ~4095ull;
-   else
-      map_offset = 0;
-   assert(offset >= map_offset);
-   uint64_t map_size = (offset + size) - map_offset;
-
-   /* Let's map whole pages */
-   map_size = align64(map_size, 4096);
+   uint64_t map_offset, map_size;
+   anv_sanitize_map_params(device, offset, size, &map_offset, &map_size);
 
    void *map;
    VkResult result = anv_device_map_bo(device, mem->bo, map_offset,
diff --git a/src/intel/vulkan/anv_private.h b/src/intel/vulkan/anv_private.h
index a42d2d3bdb5..b1d8a5df1ae 100644
--- a/src/intel/vulkan/anv_private.h
+++ b/src/intel/vulkan/anv_private.h
@@ -2149,6 +2149,26 @@ anv_mocs_for_address(const struct anv_device *device,
 void anv_device_init_blorp(struct anv_device *device);
 void anv_device_finish_blorp(struct anv_device *device);
 
+static inline void
+anv_sanitize_map_params(struct anv_device *device,
+                        uint64_t in_offset,
+                        uint64_t in_size,
+                        uint64_t *out_offset,
+                        uint64_t *out_size)
+{
+   /* GEM will fail to map if the offset isn't 4k-aligned.  Round down. */
+   if (!device->physical->info.has_mmap_offset)
+      *out_offset = in_offset & ~4095ull;
+   else
+      *out_offset = 0;
+   assert(in_offset >= *out_offset);
+   *out_size = (in_offset + in_size) - *out_offset;
+
+   /* Let's map whole pages */
+   *out_size = align64(*out_size, 4096);
+}
+
+
 VkResult anv_device_alloc_bo(struct anv_device *device,
                              const char *name, uint64_t size,
                              enum anv_bo_alloc_flags alloc_flags,