s390/mem_detect: do not truncate online memory ranges info

Commit bf64f05 ("s390/mem_detect: handle online memory limit
just once") introduced truncation of mem_detect online ranges
based on identity mapping size. For kdump case however the full
set of online memory ranges has to be feed into memblock_physmem_add
so that crashed system memory could be extracted.

Instead of truncating introduce a "usable limit" which is respected by
mem_detect api. Also add extra online memory ranges iterator which still
provides full set of online memory ranges disregarding the "usable limit".

Fixes: bf64f05 ("s390/mem_detect: handle online memory limit just once")
Reported-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Tested-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

Author: Vasily Gorbik

arch/s390/boot/boot.h

@@ -34,7 +34,7 @@ struct vmlinux_info {
 
 void startup_kernel(void);
 unsigned long detect_memory(unsigned long *safe_addr);
-void mem_detect_truncate(unsigned long limit);
+void mem_detect_set_usable_limit(unsigned long limit);
 bool is_ipl_block_dump(void);
 void store_ipl_parmblock(void);
 unsigned long read_ipl_report(unsigned long safe_addr);

arch/s390/boot/kaslr.c

@@ -132,7 +132,7 @@ static unsigned long count_valid_kernel_positions(unsigned long kernel_size,
 	unsigned long start, end, pos = 0;
 	int i;
 
-	for_each_mem_detect_block(i, &start, &end) {
+	for_each_mem_detect_usable_block(i, &start, &end) {
 		if (_min >= end)
 			continue;
 		if (start >= _max)
@@ -153,7 +153,7 @@ static unsigned long position_to_address(unsigned long pos, unsigned long kernel
 	unsigned long start, end;
 	int i;
 
-	for_each_mem_detect_block(i, &start, &end) {
+	for_each_mem_detect_usable_block(i, &start, &end) {
 		if (_min >= end)
 			continue;
 		if (start >= _max)
@@ -172,7 +172,7 @@ static unsigned long position_to_address(unsigned long pos, unsigned long kernel
 
 unsigned long get_random_base(unsigned long safe_addr)
 {
-	unsigned long online_mem_total = get_mem_detect_online_total();
+	unsigned long usable_total = get_mem_detect_usable_total();
 	unsigned long memory_limit = get_mem_detect_end();
 	unsigned long base_pos, max_pos, kernel_size;
 	int i;
@@ -182,8 +182,8 @@ unsigned long get_random_base(unsigned long safe_addr)
 	 * which vmem and kasan code will use for shadow memory and
 	 * pgtable mapping allocations.
 	 */
-	memory_limit -= kasan_estimate_memory_needs(online_mem_total);
-	memory_limit -= vmem_estimate_memory_needs(online_mem_total);
+	memory_limit -= kasan_estimate_memory_needs(usable_total);
+	memory_limit -= vmem_estimate_memory_needs(usable_total);
 
 	safe_addr = ALIGN(safe_addr, THREAD_SIZE);
 	kernel_size = vmlinux.image_size + vmlinux.bss_size;

arch/s390/boot/mem_detect.c

@@ -172,20 +172,20 @@ unsigned long detect_memory(unsigned long *safe_addr)
 	return max_physmem_end;
 }
 
-void mem_detect_truncate(unsigned long limit)
+void mem_detect_set_usable_limit(unsigned long limit)
 {
 	struct mem_detect_block *block;
 	int i;
 
+	/* make sure mem_detect.usable ends up within online memory block */
 	for (i = 0; i < mem_detect.count; i++) {
 		block = __get_mem_detect_block_ptr(i);
-		if (block->start >= limit) {
-			mem_detect.count = i;
+		if (block->start >= limit)
 			break;
-		} else if (block->end > limit) {
-			block->end = (u64)limit;
-			mem_detect.count = i + 1;
+		if (block->end >= limit) {
+			mem_detect.usable = limit;
 			break;
 		}
+		mem_detect.usable = block->end;
 	}
 }

arch/s390/boot/startup.c

@@ -304,7 +304,7 @@ void startup_kernel(void)
 	setup_ident_map_size(max_physmem_end);
 	setup_vmalloc_size();
 	asce_limit = setup_kernel_memory_layout();
-	mem_detect_truncate(ident_map_size);
+	mem_detect_set_usable_limit(ident_map_size);
 
 	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && kaslr_enabled) {
 		random_lma = get_random_base(safe_addr);

arch/s390/boot/vmem.c

@@ -252,7 +252,7 @@ void setup_vmem(unsigned long asce_limit)
 	 */
 	pgtable_populate_init();
 	pgtable_populate(0, sizeof(struct lowcore), POPULATE_ONE2ONE);
-	for_each_mem_detect_block(i, &start, &end)
+	for_each_mem_detect_usable_block(i, &start, &end)
 		pgtable_populate(start, end, POPULATE_ONE2ONE);
 	pgtable_populate(__abs_lowcore, __abs_lowcore + sizeof(struct lowcore),
 			 POPULATE_ABS_LOWCORE);

arch/s390/include/asm/mem_detect.h

@@ -30,6 +30,7 @@ struct mem_detect_block {
 struct mem_detect_info {
 	u32 count;
 	u8 info_source;
+	unsigned long usable;
 	struct mem_detect_block entries[MEM_INLINED_ENTRIES];
 	struct mem_detect_block *entries_extended;
 };
@@ -38,7 +39,7 @@ extern struct mem_detect_info mem_detect;
 void add_mem_detect_block(u64 start, u64 end);
 
 static inline int __get_mem_detect_block(u32 n, unsigned long *start,
-					 unsigned long *end)
+					 unsigned long *end, bool respect_usable_limit)
 {
 	if (n >= mem_detect.count) {
 		*start = 0;
@@ -53,28 +54,37 @@ static inline int __get_mem_detect_block(u32 n, unsigned long *start,
 		*start = (unsigned long)mem_detect.entries_extended[n - MEM_INLINED_ENTRIES].start;
 		*end = (unsigned long)mem_detect.entries_extended[n - MEM_INLINED_ENTRIES].end;
 	}
+
+	if (respect_usable_limit && mem_detect.usable) {
+		if (*start >= mem_detect.usable)
+			return -1;
+		if (*end > mem_detect.usable)
+			*end = mem_detect.usable;
+	}
 	return 0;
 }
 
 /**
- * for_each_mem_detect_block - early online memory range iterator
+ * for_each_mem_detect_usable_block - early online memory range iterator
  * @i: an integer used as loop variable
  * @p_start: ptr to unsigned long for start address of the range
  * @p_end: ptr to unsigned long for end address of the range
  *
- * Walks over detected online memory ranges.
+ * Walks over detected online memory ranges below usable limit.
  */
-#define for_each_mem_detect_block(i, p_start, p_end)			\
-	for (i = 0, __get_mem_detect_block(i, p_start, p_end);		\
-	     i < mem_detect.count;					\
-	     i++, __get_mem_detect_block(i, p_start, p_end))
+#define for_each_mem_detect_usable_block(i, p_start, p_end)		\
+	for (i = 0; !__get_mem_detect_block(i, p_start, p_end, true); i++)
+
+/* Walks over all detected online memory ranges disregarding usable limit. */
+#define for_each_mem_detect_block(i, p_start, p_end)		\
+	for (i = 0; !__get_mem_detect_block(i, p_start, p_end, false); i++)
 
-static inline unsigned long get_mem_detect_online_total(void)
+static inline unsigned long get_mem_detect_usable_total(void)
 {
 	unsigned long start, end, total = 0;
 	int i;
 
-	for_each_mem_detect_block(i, &start, &end)
+	for_each_mem_detect_usable_block(i, &start, &end)
 		total += end - start;
 
 	return total;
@@ -95,8 +105,10 @@ static inline unsigned long get_mem_detect_end(void)
 	unsigned long start;
 	unsigned long end;
 
+	if (mem_detect.usable)
+		return mem_detect.usable;
 	if (mem_detect.count) {
-		__get_mem_detect_block(mem_detect.count - 1, &start, &end);
+		__get_mem_detect_block(mem_detect.count - 1, &start, &end, false);
 		return end;
 	}
 	return 0;

arch/s390/kernel/setup.c

@@ -772,10 +772,10 @@ static void __init memblock_add_mem_detect_info(void)
 		 get_mem_info_source(), mem_detect.info_source);
 	/* keep memblock lists close to the kernel */
 	memblock_set_bottom_up(true);
-	for_each_mem_detect_block(i, &start, &end) {
+	for_each_mem_detect_usable_block(i, &start, &end)
 		memblock_add(start, end - start);
+	for_each_mem_detect_block(i, &start, &end)
 		memblock_physmem_add(start, end - start);
-	}
 	memblock_set_bottom_up(false);
 	memblock_set_node(0, ULONG_MAX, &memblock.memory, 0);
 }

arch/s390/mm/kasan_init.c

@@ -244,7 +244,7 @@ void __init kasan_early_init(void)
 	memset64((u64 *)kasan_early_shadow_pte, pte_val(pte_z), PTRS_PER_PTE);
 
 	if (has_edat) {
-		shadow_alloc_size = get_mem_detect_online_total() >> KASAN_SHADOW_SCALE_SHIFT;
+		shadow_alloc_size = get_mem_detect_usable_total() >> KASAN_SHADOW_SCALE_SHIFT;
 		segment_pos = round_down(pgalloc_pos, _SEGMENT_SIZE);
 		segment_low = segment_pos - shadow_alloc_size;
 		segment_low = round_down(segment_low, _SEGMENT_SIZE);
@@ -282,7 +282,7 @@ void __init kasan_early_init(void)
 	 * +- shadow end ----+---------+- shadow end ---+
 	 */
 	/* populate kasan shadow (for identity mapping and zero page mapping) */
-	for_each_mem_detect_block(i, &start, &end)
+	for_each_mem_detect_usable_block(i, &start, &end)
 		kasan_early_pgtable_populate(__sha(start), __sha(end), POPULATE_MAP);
 	if (IS_ENABLED(CONFIG_KASAN_VMALLOC)) {
 		untracked_end = VMALLOC_START;