xen/arm: Introduce fw_unreserved_regions() and use it

Since commit 6e3e771203 "xen/arm: setup: Relocate the Device-Tree
later on in the boot", the device-tree will not be kept mapped when
using ACPI.

However, a few places are calling dt_unreserved_regions() which expects
a valid DT. This will lead to a crash.

As the DT should not be used for ACPI (other than for detecting the
modules), a new function fw_unreserved_regions() is introduced.

It will behave the same way on DT system. On ACPI system, it will
unreserve the whole region.

Take the opportunity to clarify that bootinfo.reserved_mem is only used
when booting using Device-Tree.

Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

xen/arch/arm/kernel.c

@@ -307,7 +307,7 @@ static __init int kernel_decompress(struct bootmodule *mod)
      * Free the original kernel, update the pointers to the
      * decompressed kernel
      */
-    dt_unreserved_regions(addr, addr + size, init_domheap_pages, 0);
+    fw_unreserved_regions(addr, addr + size, init_domheap_pages, 0);
 
     return 0;
 }

xen/arch/arm/setup.c

@@ -196,8 +196,9 @@ static void __init processor_id(void)
     processor_setup();
 }
 
-void __init dt_unreserved_regions(paddr_t s, paddr_t e,
-                                  void (*cb)(paddr_t, paddr_t), int first)
+static void __init dt_unreserved_regions(paddr_t s, paddr_t e,
+                                         void (*cb)(paddr_t, paddr_t),
+                                         int first)
 {
     int i, nr = fdt_num_mem_rsv(device_tree_flattened);
 
@@ -244,6 +245,17 @@ void __init dt_unreserved_regions(paddr_t s, paddr_t e,
     cb(s, e);
 }
 
+void __init fw_unreserved_regions(paddr_t s, paddr_t e,
+                                  void (*cb)(paddr_t, paddr_t), int first)
+{
+    if ( acpi_disabled )
+        dt_unreserved_regions(s, e, cb, first);
+    else
+        cb(s, e);
+}
+
+
+
 struct bootmodule __init *add_boot_module(bootmodule_kind kind,
                                           paddr_t start, paddr_t size,
                                           bool domU)
@@ -405,7 +417,7 @@ void __init discard_initial_modules(void)
              !mfn_valid(maddr_to_mfn(e)) )
             continue;
 
-        dt_unreserved_regions(s, e, init_domheap_pages, 0);
+        fw_unreserved_regions(s, e, init_domheap_pages, 0);
     }
 
     mi->nr_mods = 0;
@@ -712,7 +724,7 @@ static void __init setup_mm(void)
                 n = mfn_to_maddr(mfn_add(xenheap_mfn_start, xenheap_pages));
             }
 
-            dt_unreserved_regions(s, e, init_boot_pages, 0);
+            fw_unreserved_regions(s, e, init_boot_pages, 0);
 
             s = n;
         }
@@ -765,7 +777,7 @@ static void __init setup_mm(void)
             if ( e > bank_end )
                 e = bank_end;
 
-            dt_unreserved_regions(s, e, init_boot_pages, 0);
+            fw_unreserved_regions(s, e, init_boot_pages, 0);
             s = n;
         }
     }

xen/include/asm-arm/setup.h

@@ -67,6 +67,7 @@ struct bootcmdlines {
 
 struct bootinfo {
     struct meminfo mem;
+    /* The reserved regions are only used when booting using Device-Tree */
     struct meminfo reserved_mem;
     struct bootmodules modules;
     struct bootcmdlines cmdlines;
@@ -96,7 +97,7 @@ int construct_dom0(struct domain *d);
 void create_domUs(void);
 
 void discard_initial_modules(void);
-void dt_unreserved_regions(paddr_t s, paddr_t e,
+void fw_unreserved_regions(paddr_t s, paddr_t e,
                            void (*cb)(paddr_t, paddr_t), int first);
 
 size_t boot_fdt_info(const void *fdt, paddr_t paddr);