Xen maps the virtual memory space starting from L0 slot 4, so it's open
coded for macros with the offset '4'.

For more readable, add a new macro XEN_VM_MAPPING which defines the
start slot for Xen virtual memory mapping, and all virtual memory
regions are defined based on it.

Acked-by: Julien Grall <jgrall@amazon.com>
Signed-off-by: Leo Yan <leo.yan@linaro.org>
---
 xen/arch/arm/include/asm/mmu/layout.h | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/xen/arch/arm/include/asm/mmu/layout.h b/xen/arch/arm/include/asm/mmu/layout.h
index da6be276ac..2cb2382fbf 100644
--- a/xen/arch/arm/include/asm/mmu/layout.h
+++ b/xen/arch/arm/include/asm/mmu/layout.h
@@ -49,11 +49,14 @@
 #define XEN_VIRT_START          _AT(vaddr_t, MB(2))
 #else
 
+#define IDENTITY_MAPPING_AREA_NR_L0     4
+#define XEN_VM_MAPPING                  SLOT0(IDENTITY_MAPPING_AREA_NR_L0)
+
 #define SLOT0_ENTRY_BITS  39
 #define SLOT0(slot) (_AT(vaddr_t,slot) << SLOT0_ENTRY_BITS)
 #define SLOT0_ENTRY_SIZE  SLOT0(1)
 
-#define XEN_VIRT_START          (SLOT0(4) + _AT(vaddr_t, MB(2)))
+#define XEN_VIRT_START          (XEN_VM_MAPPING + _AT(vaddr_t, MB(2)))
 #endif
 
 /*
@@ -116,12 +119,10 @@
 
 #else /* ARM_64 */
 
-#define IDENTITY_MAPPING_AREA_NR_L0  4
-
-#define VMAP_VIRT_START  (SLOT0(4) + GB(1))
+#define VMAP_VIRT_START  (XEN_VM_MAPPING + GB(1))
 #define VMAP_VIRT_SIZE   GB(1)
 
-#define FRAMETABLE_VIRT_START  (SLOT0(4) + GB(32))
+#define FRAMETABLE_VIRT_START  (XEN_VM_MAPPING + GB(32))
 #define FRAMETABLE_SIZE        GB(32)
 #define FRAMETABLE_NR          (FRAMETABLE_SIZE / sizeof(*frame_table))
 
-- 
2.39.2