2 files changed, 39 insertions, 7 deletions

diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index d0335853ff52..fc1d579f212b 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -19,6 +19,7 @@
 #include <linux/mm.h>
 #include <linux/pfn.h>
 #include <linux/suspend.h>
+#include <linux/firmware-map.h>
 
 #include <asm/pgtable.h>
 #include <asm/page.h>
@@ -27,7 +28,22 @@
 #include <asm/setup.h>
 #include <asm/trampoline.h>
 
+/*
+ * The e820 map is the map that gets modified e.g. with command line parameters
+ * and that is also registered with modifications in the kernel resource tree
+ * with the iomem_resource as parent.
+ *
+ * The e820_saved is directly saved after the BIOS-provided memory map is
+ * copied. It doesn't get modified afterwards. It's registered for the
+ * /sys/firmware/memmap interface.
+ *
+ * That memory map is not modified and is used as base for kexec. The kexec'd
+ * kernel should get the same memory map as the firmware provides. Then the
+ * user can e.g. boot the original kernel with mem=1G while still booting the
+ * next kernel with full memory.
+ */
 struct e820map e820;
+struct e820map e820_saved;
 
 /* For PCI or other memory-mapped resources */
 unsigned long pci_mem_start = 0xaeedbabe;
@@ -1198,6 +1214,17 @@ void __init finish_e820_parsing(void)
         }
 }
 
+static inline const char *e820_type_to_string(int e820_type)
+{
+        switch (e820_type) {
+        case E820_RESERVED_KERN:
+        case E820_RAM:  return "System RAM";
+        case E820_ACPI: return "ACPI Tables";
+        case E820_NVS:  return "ACPI Non-volatile Storage";
+        default:        return "reserved";
+        }
+}
+
 /*
  * Mark e820 reserved areas as busy for the resource manager.
  */
@@ -1209,13 +1236,6 @@ void __init e820_reserve_resources(void)
 
         res = alloc_bootmem_low(sizeof(struct resource) * e820.nr_map);
         for (i = 0; i < e820.nr_map; i++) {
-                switch (e820.map[i].type) {
-                case E820_RESERVED_KERN:
-                case E820_RAM:  res->name = "System RAM"; break;
-                case E820_ACPI: res->name = "ACPI Tables"; break;
-                case E820_NVS:  res->name = "ACPI Non-volatile Storage"; break;
-                default:        res->name = "reserved";
-                }
                 end = e820.map[i].addr + e820.map[i].size - 1;
 #ifndef CONFIG_RESOURCES_64BIT
                 if (end > 0x100000000ULL) {
@@ -1223,6 +1243,7 @@ void __init e820_reserve_resources(void)
                         continue;
                 }
 #endif
+                res->name = e820_type_to_string(e820.map[i].type);
                 res->start = e820.map[i].addr;
                 res->end = end;
 
@@ -1230,6 +1251,13 @@ void __init e820_reserve_resources(void)
                 insert_resource(&iomem_resource, res);
                 res++;
         }
+
+        for (i = 0; i < e820_saved.nr_map; i++) {
+                struct e820entry *entry = &e820_saved.map[i];
+                firmware_map_add_early(entry->addr,
+                        entry->addr + entry->size - 1,
+                        e820_type_to_string(entry->type));
+        }
 }
 
 char *__init default_machine_specific_memory_setup(void)
@@ -1266,6 +1294,8 @@ char *__init default_machine_specific_memory_setup(void)
                 e820_add_region(HIGH_MEMORY, mem_size << 10, E820_RAM);
         }
 
+        memcpy(&e820_saved, &e820, sizeof(struct e820map));
+
         /* In case someone cares... */
         return who;
 }
diff --git a/include/asm-x86/e820.h b/include/asm-x86/e820.h
index 4b26604b3c19..a20d0a7f5892 100644
--- a/include/asm-x86/e820.h
+++ b/include/asm-x86/e820.h
@@ -59,7 +59,9 @@ struct e820map {
         struct e820entry map[E820_X_MAX];
 };
 
+/* see comment in arch/x86/kernel/e820.c */
 extern struct e820map e820;
+extern struct e820map e820_saved;
 
 extern int e820_any_mapped(u64 start, u64 end, unsigned type);
 extern int e820_all_mapped(u64 start, u64 end, unsigned type);