[PATCH v5 23/31] 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, 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 |  150 +++++++++++++++++++++++++++++++++++++++---
 1 file changed, 138 insertions(+), 12 deletions(-)

diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
index 2dd4621..3981599 100644
--- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c
@@ -37,6 +37,7 @@ static struct fw_dump fw_dump;
 
 static DEFINE_MUTEX(fadump_mutex);
 struct fadump_mrange_info crash_mrange_info = { "crash", NULL, 0, 0, 0 };
+struct fadump_mrange_info reserved_mrange_info = { "reserved", NULL, 0, 0, 0 };
 
 #ifdef CONFIG_CMA
 static struct cma *fadump_cma;
@@ -881,33 +882,158 @@ 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.
+ * Sort the mem ranges in-place and merge adjacent ranges
+ * to minimize the memory ranges count.
+ */
+static void sort_and_merge_mem_ranges(struct fadump_mrange_info *mrange_info)
+{
+	unsigned long long base, size;
+	struct fadump_memory_range tmp_range;
+	struct fadump_memory_range *mem_ranges;
+	int i, j, idx;
+
+	if (!reserved_mrange_info.mem_range_cnt)
+		return;
+
+	/* Sort the memory ranges */
+	mem_ranges = mrange_info->mem_ranges;
+	for (i = 0; i < mrange_info->mem_range_cnt; i++) {
+		idx = i;
+		for (j = i + 1; j < mrange_info->mem_range_cnt; j++) {
+			if (mem_ranges[idx].base > mem_ranges[j].base)
+				idx = j;
+		}
+		if (idx != i) {
+			tmp_range = mem_ranges[idx];
+			mem_ranges[idx] = mem_ranges[i];
+			mem_ranges[i] = tmp_range;
+		}
+	}
+
+	/* Merge adjacent reserved ranges */
+	idx = 0;
+	for (i = 1; i < mrange_info->mem_range_cnt; i++) {
+		base = mem_ranges[i-1].base;
+		size = mem_ranges[i-1].size;
+		if (mem_ranges[i].base == (base + size))
+			mem_ranges[idx].size += mem_ranges[i].size;
+		else {
+			idx++;
+			if (i == idx)
+				continue;
+
+			mem_ranges[idx] = mem_ranges[i];
+		}
+	}
+	mrange_info->mem_range_cnt = idx + 1;
+}
+
+/*
+ * Scan reserved-ranges to consider them while reserving/releasing
+ * memory for FADump.
+ */
+static inline int fadump_scan_reserved_mem_ranges(void)
+{
+	int len, ret = -1;
+	unsigned long i;
+	const __be32 *prop;
+	struct device_node *root;
+
+	root = of_find_node_by_path("/");
+	if (!root)
+		return ret;
+
+	prop = of_get_property(root, "reserved-ranges", &len);
+	if (!prop)
+		return ret;
+
+	/*
+	 * Each reserved range is an (address,size) pair, 2 cells each,
+	 * totalling 4 cells per range.
+	 */
+	for (i = 0; i < len / (sizeof(*prop) * 4); i++) {
+		u64 base, size;
+
+		base = of_read_number(prop + (i * 4) + 0, 2);
+		size = of_read_number(prop + (i * 4) + 2, 2);
+
+		if (size) {
+			ret = fadump_add_mem_range(&reserved_mrange_info,
+						   base, base + size);
+			if (ret < 0) {
+				pr_warn("some reserved ranges are ignored!\n");
+				break;
+			}
+		}
+	}
+
+	return ret;
+}
+
+/*
+ * 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, ret;
 	unsigned long ra_start, ra_end;
+	unsigned long tstart;
+
+	fadump_scan_reserved_mem_ranges();
 
 	ra_start = fw_dump.reserve_dump_area_start;
 	ra_end = ra_start + fw_dump.reserve_dump_area_size;
 
 	/*
-	 * exclude the dump reserve area. Will reuse it for next
-	 * fadump registration.
+	 * Add reserved dump area 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);
+	ret = fadump_add_mem_range(&reserved_mrange_info, ra_start, ra_end);
+	if (ret != 0) {
+		/*
+		 * Not enough memory to setup reserved ranges but the system is
+		 * running shortage of memory. So, release all the memory except
+		 * Reserved dump area (reused for next fadump registration).
+		 */
+		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);
+
+		return;
+	}
+
+	/* Get the reserved ranges list in order first. */
+	sort_and_merge_mem_ranges(&reserved_mrange_info);
+
+	/* Exclude reserved ranges and release remaining memory */
+	tstart = begin;
+	for (i = 0; i < reserved_mrange_info.mem_range_cnt; i++) {
+		ra_start = reserved_mrange_info.mem_ranges[i].base;
+		ra_end = ra_start + reserved_mrange_info.mem_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)