xen: arm: Add a new helper update_boot_mapping()

update_boot_mapping() invokes update_identity_mapping() for the MMU specific
code.
Later when the MPU code is added, update_boot_mapping() will invoke the
equivalent.

The common code now invokes update_boot_mapping() instead of
update_identity_mapping(). So, that there is clear abstraction between the
common and MMU/MPU specific logic.

This is in continuation to commit
f661a20aa8: "Extract MMU-specific MM code".

update_identity_mapping() is now marked as static as it is called from
xen/arch/arm/arm64/mmu/mm.c only. Also, amend the prototype to
update_boot_mapping() which is now invoked from other files.

Signed-off-by: Ayan Kumar Halder <ayan.kumar.halder@amd.com>
Reviewed-by: Michal Orzel <michal.orzel@amd.com>

xen/arch/arm/arm64/mmu/mm.c

@@ -111,7 +111,14 @@ void __init arch_setup_page_tables(void)
     prepare_runtime_identity_mapping();
 }
 
-void update_identity_mapping(bool enable)
+/*
+ * Enable/disable the identity mapping in the live page-tables (i.e.
+ * the one pointed by TTBR_EL2).
+ *
+ * Note that nested call (e.g. enable=true, enable=true) is not
+ * supported.
+ */
+static void update_identity_mapping(bool enable)
 {
     paddr_t id_addr = virt_to_maddr(_start);
     int rc;
@@ -125,6 +132,11 @@ void update_identity_mapping(bool enable)
     BUG_ON(rc);
 }
 
+void update_boot_mapping(bool enable)
+{
+    update_identity_mapping(enable);
+}
+
 extern void switch_ttbr_id(uint64_t ttbr);
 
 typedef void (switch_ttbr_fn)(uint64_t ttbr);

xen/arch/arm/arm64/smpboot.c

@@ -112,18 +112,18 @@ int arch_cpu_up(int cpu)
     if ( !smp_enable_ops[cpu].prepare_cpu )
         return -ENODEV;
 
-    update_identity_mapping(true);
+    update_boot_mapping(true);
 
     rc = smp_enable_ops[cpu].prepare_cpu(cpu);
     if ( rc )
-        update_identity_mapping(false);
+        update_boot_mapping(false);
 
     return rc;
 }
 
 void arch_cpu_up_finish(void)
 {
-    update_identity_mapping(false);
+    update_boot_mapping(false);
 }
 
 /*

xen/arch/arm/include/asm/arm64/mm.h

@@ -14,14 +14,7 @@ static inline bool arch_mfns_in_directmap(unsigned long mfn, unsigned long nr)
 
 void arch_setup_page_tables(void);
 
-/*
- * Enable/disable the identity mapping in the live page-tables (i.e.
- * the one pointed by TTBR_EL2).
- *
- * Note that nested call (e.g. enable=true, enable=true) is not
- * supported.
- */
-void update_identity_mapping(bool enable);
+void update_boot_mapping(bool enable);
 
 #endif /* __ARM_ARM64_MM_H__ */