powerpc/fadump: release all the memory above boot memory size

Except for Reserved dump area (see Documentation/powerpc/firmware-
assisted-dump.rst) which is permanent reserved, all memory above boot
memory size, where boot memory size is the memory required for the
kernel to boot successfully when booted with restricted memory (memory
for capture kernel), is released when the dump is invalidated. Make
this a bit more explicit in the code.
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/156821336092.5656.1079046285366041687.stgit@hbathini.in.ibm.com

arch/powerpc/kernel/fadump.c

@@ -391,6 +391,8 @@ int __init fadump_reserve_mem(void)
 	else
 		memory_boundary = memblock_end_of_DRAM();
 
+	size = get_fadump_area_size();
+	fw_dump.reserve_dump_area_size = size;
 	if (fw_dump.dump_active) {
 		pr_info("Firmware-assisted dump is active.\n");
 
@@ -416,11 +418,14 @@ int __init fadump_reserve_mem(void)
 				be64_to_cpu(fdm_active->rmr_region.destination_address) +
 				be64_to_cpu(fdm_active->rmr_region.source_len);
 		pr_debug("fadumphdr_addr = %pa\n", &fw_dump.fadumphdr_addr);
-		fw_dump.reserve_dump_area_start = base;
-		fw_dump.reserve_dump_area_size = size;
-	} else {
-		size = get_fadump_area_size();
 
+		/*
+		 * Start address of reserve dump area (permanent reservation)
+		 * for re-registering FADump after dump capture.
+		 */
+		fw_dump.reserve_dump_area_start =
+			be64_to_cpu(fdm_active->cpu_state_data.destination_address);
+	} else {
 		/*
 		 * Reserve memory at an offset closer to bottom of the RAM to
 		 * minimize the impact of memory hot-remove operation. We can't
@@ -447,7 +452,6 @@ int __init fadump_reserve_mem(void)
 			(unsigned long)(memblock_phys_mem_size() >> 20));
 
 		fw_dump.reserve_dump_area_start = base;
-		fw_dump.reserve_dump_area_size = size;
 		return fadump_cma_init();
 	}
 	return 1;
@@ -1265,34 +1269,16 @@ static void fadump_release_memory(unsigned long begin, unsigned long end)
 
 static void fadump_invalidate_release_mem(void)
 {
-	unsigned long reserved_area_start, reserved_area_end;
-	unsigned long destination_address;
-
 	mutex_lock(&fadump_mutex);
 	if (!fw_dump.dump_active) {
 		mutex_unlock(&fadump_mutex);
 		return;
 	}
 
-	destination_address = be64_to_cpu(fdm_active->cpu_state_data.destination_address);
 	fadump_cleanup();
 	mutex_unlock(&fadump_mutex);
 
-	/*
-	 * Save the current reserved memory bounds we will require them
-	 * later for releasing the memory for general use.
-	 */
-	reserved_area_start = fw_dump.reserve_dump_area_start;
-	reserved_area_end = reserved_area_start +
-			fw_dump.reserve_dump_area_size;
-	/*
-	 * Setup reserve_dump_area_start and its size so that we can
-	 * reuse this reserved memory for Re-registration.
-	 */
-	fw_dump.reserve_dump_area_start = destination_address;
-	fw_dump.reserve_dump_area_size = get_fadump_area_size();
-
-	fadump_release_memory(reserved_area_start, reserved_area_end);
+	fadump_release_memory(fw_dump.boot_memory_size, memblock_end_of_DRAM());
 	fadump_free_cpu_notes_buf();
 
 	/* Initialize the kernel dump memory structure for FAD registration. */