s390/mem_detect: handle online memory limit just once

Introduce mem_detect_truncate() to cut any online memory ranges above
established identity mapping size, so that mem_detect users wouldn't
have to do it over and over again.

Suggested-by: Alexander Gordeev <agordeev@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>

arch/s390/boot/boot.h

@@ -34,6 +34,7 @@ struct vmlinux_info {
 
 void startup_kernel(void);
 unsigned long detect_memory(unsigned long *safe_addr);
+void mem_detect_truncate(unsigned long limit);
 bool is_ipl_block_dump(void);
 void store_ipl_parmblock(void);
 unsigned long read_ipl_report(unsigned long safe_addr);
@@ -44,7 +45,7 @@ void print_missing_facilities(void);
 void sclp_early_setup_buffer(void);
 void print_pgm_check_info(void);
 unsigned long get_random_base(unsigned long safe_addr);
-void setup_vmem(unsigned long ident_map_size, unsigned long asce_limit);
+void setup_vmem(unsigned long asce_limit);
 void __printf(1, 2) decompressor_printk(const char *fmt, ...);
 void error(char *m);
 

arch/s390/boot/kaslr.c

@@ -176,8 +176,6 @@ unsigned long get_random_base(unsigned long safe_addr)
 	unsigned long base_pos, max_pos, kernel_size;
 	int i;
 
-	memory_limit = min(memory_limit, ident_map_size);
-
 	/*
 	 * Avoid putting kernel in the end of physical memory
 	 * which kasan will use for shadow memory and early pgtable

arch/s390/boot/mem_detect.c

@@ -171,3 +171,21 @@ unsigned long detect_memory(unsigned long *safe_addr)
 
 	return max_physmem_end;
 }
+
+void mem_detect_truncate(unsigned long limit)
+{
+	struct mem_detect_block *block;
+	int i;
+
+	for (i = 0; i < mem_detect.count; i++) {
+		block = __get_mem_detect_block_ptr(i);
+		if (block->start >= limit) {
+			mem_detect.count = i;
+			break;
+		} else if (block->end > limit) {
+			block->end = (u64)limit;
+			mem_detect.count = i + 1;
+			break;
+		}
+	}
+}

arch/s390/boot/startup.c

@@ -305,6 +305,7 @@ 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);
 
 	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && kaslr_enabled) {
 		random_lma = get_random_base(safe_addr);
@@ -336,7 +337,7 @@ void startup_kernel(void)
 	 */
 	clear_bss_section();
 	handle_relocs(__kaslr_offset);
-	setup_vmem(ident_map_size, asce_limit);
+	setup_vmem(asce_limit);
 	copy_bootdata();
 
 	if (__kaslr_offset) {

arch/s390/boot/vmem.c

@@ -39,7 +39,7 @@ static void boot_check_oom(void)
 		error("out of memory on boot\n");
 }
 
-static void pgtable_populate_init(unsigned long ident_map_size)
+static void pgtable_populate_init(void)
 {
 	unsigned long initrd_end;
 	unsigned long kernel_end;
@@ -51,7 +51,7 @@ static void pgtable_populate_init(unsigned long ident_map_size)
 		pgalloc_low = max(pgalloc_low, initrd_end);
 	}
 
-	pgalloc_end = round_down(min(ident_map_size, get_mem_detect_end()), PAGE_SIZE);
+	pgalloc_end = round_down(get_mem_detect_end(), PAGE_SIZE);
 	pgalloc_pos = pgalloc_end;
 
 	boot_check_oom();
@@ -226,7 +226,7 @@ static void pgtable_populate(unsigned long addr, unsigned long end, enum populat
 	}
 }
 
-void setup_vmem(unsigned long ident_map_size, unsigned long asce_limit)
+void setup_vmem(unsigned long asce_limit)
 {
 	unsigned long start, end;
 	unsigned long asce_type;
@@ -250,13 +250,10 @@ void setup_vmem(unsigned long ident_map_size, unsigned long asce_limit)
 	 * To prevent creation of a large page at address 0 first map
 	 * the lowcore and create the identity mapping only afterwards.
 	 */
-	pgtable_populate_init(ident_map_size);
+	pgtable_populate_init();
 	pgtable_populate(0, sizeof(struct lowcore), POPULATE_ONE2ONE);
-	for_each_mem_detect_block(i, &start, &end) {
-		if (start >= ident_map_size)
-			break;
-		pgtable_populate(start, min(end, ident_map_size), POPULATE_ONE2ONE);
-	}
+	for_each_mem_detect_block(i, &start, &end)
+		pgtable_populate(start, end, POPULATE_ONE2ONE);
 	pgtable_populate(__abs_lowcore, __abs_lowcore + sizeof(struct lowcore),
 			 POPULATE_ABS_LOWCORE);
 	pgtable_populate(__memcpy_real_area, __memcpy_real_area + PAGE_SIZE,

arch/s390/kernel/setup.c

@@ -600,7 +600,6 @@ static void __init setup_resources(void)
 
 static void __init setup_memory_end(void)
 {
-	memblock_remove(ident_map_size, PHYS_ADDR_MAX - ident_map_size);
 	max_pfn = max_low_pfn = PFN_DOWN(ident_map_size);
 	pr_notice("The maximum memory size is %luMB\n", ident_map_size >> 20);
 }

arch/s390/mm/kasan_init.c

@@ -247,8 +247,6 @@ void __init kasan_early_init(void)
 	 * The rest [memsize, ident_map_size] if memsize < ident_map_size
 	 * could be mapped/unmapped dynamically later during memory hotplug.
 	 */
-	memsize = min(memsize, ident_map_size);
-
 	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, P4D_SIZE));
 	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, P4D_SIZE));