[PATCH v2 08/16] powerpc/fadump: consider reserved ranges while releasing memory

[Hari Bathini <hbathini@linux.ibm.com>]

Commit 0962e8004e97 ("powerpc/prom: Scan reserved-ranges node for
memory reservations") enabled support to parse 'reserved-ranges' DT
node to reserve kernel memory falling in these ranges for firmware
purposes. Along with the preserved area memory, also ensure memory
in reserved ranges is not overlapped with memory released by capture
kernel aftering saving vmcore. Also, fix the off-by-one error in
fadump_release_reserved_area function while releasing memory.

Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
---
 arch/powerpc/kernel/fadump.c |   59 +++++++++++++++++++++++++++++-------------
 1 file changed, 41 insertions(+), 18 deletions(-)

diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
index 39b6670..fd06571 100644
--- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c
@@ -123,7 +123,7 @@ static int __init fadump_cma_init(void) { return 1; }
  * Sort the reserved ranges in-place and merge adjacent ranges
  * to minimize the reserved ranges count.
  */
-static void __init sort_and_merge_reserved_ranges(void)
+static void sort_and_merge_reserved_ranges(void)
 {
 	unsigned long long base, size;
 	struct fadump_memory_range tmp_range;
@@ -164,8 +164,7 @@ static void __init sort_and_merge_reserved_ranges(void)
 	reserved_ranges_cnt = idx + 1;
 }
 
-static int __init add_reserved_range(unsigned long base,
-				     unsigned long size)
+static int add_reserved_range(unsigned long base, unsigned long size)
 {
 	int i;
 
@@ -1126,33 +1125,57 @@ static void fadump_release_reserved_area(unsigned long start, unsigned long end)
 			if (tend == end_pfn)
 				break;
 
-			start_pfn = tend + 1;
+			start_pfn = tend;
 		}
 	}
 }
 
 /*
- * Release the memory that was reserved in early boot to preserve the memory
- * contents. The released memory will be available for general use.
+ * Release the memory that was reserved during early boot to preserve the
+ * crash'ed kernel's memory contents except reserved dump area (permanent
+ * reservation) and reserved ranges used by F/W. The released memory will
+ * be available for general use.
  */
 static void fadump_release_memory(unsigned long begin, unsigned long end)
 {
+	int i;
 	unsigned long ra_start, ra_end;
-
-	ra_start = fw_dump.reserve_dump_area_start;
-	ra_end = ra_start + fw_dump.reserve_dump_area_size;
+	unsigned long tstart;
 
 	/*
-	 * exclude the dump reserve area. Will reuse it for next
-	 * fadump registration.
+	 * Add memory to permanently preserve to reserved ranges list
+	 * and exclude all these ranges while releasing memory.
 	 */
-	if (begin < ra_end && end > ra_start) {
-		if (begin < ra_start)
-			fadump_release_reserved_area(begin, ra_start);
-		if (end > ra_end)
-			fadump_release_reserved_area(ra_end, end);
-	} else
-		fadump_release_reserved_area(begin, end);
+	i = add_reserved_range(fw_dump.reserve_dump_area_start,
+			       fw_dump.reserve_dump_area_size);
+	if (i == 0) {
+		/*
+		 * Reached the MAX reserved ranges count. To ensure reserved
+		 * dump area is excluded (as it will be reused for next
+		 * FADump registration), ignore the last reserved range and
+		 * add reserved dump area instead.
+		 */
+		reserved_ranges_cnt--;
+		add_reserved_range(fw_dump.reserve_dump_area_start,
+				   fw_dump.reserve_dump_area_size);
+	}
+	sort_and_merge_reserved_ranges();
+
+	tstart = begin;
+	for (i = 0; i < reserved_ranges_cnt; i++) {
+		ra_start = reserved_ranges[i].base;
+		ra_end = ra_start + reserved_ranges[i].size;
+
+		if (tstart >= ra_end)
+			continue;
+
+		if (tstart < ra_start)
+			fadump_release_reserved_area(tstart, ra_start);
+		tstart = ra_end;
+	}
+
+	if (tstart < end)
+		fadump_release_reserved_area(tstart, end);
 }
 
 static void fadump_invalidate_release_mem(void)