arm64: Add support for memmap kernel parameters

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4NYPZ
CVE: NA

-------------------------------------------------

Add support for memmap kernel parameters for ARM64. The three below
modes are supported:

memmap=exactmap
Enable setting of an exact memory map, as specified by the user.

memmap=nn[KMG]@ss[KMG]
Force usage of a specific region of memory.

memmap=nn[KMG]$ss[KMG]
Region of memory to be reserved is from ss to ss+nn, the region must
be in the range of existed memory, otherwise will be ignored.

If users set memmap=exactmap before memmap=nn[KMG]@ss[KMG], they will
get the exact memory specified by memmap=nn[KMG]@ss[KMG]. For example,
on one machine with 4GB memory, "memmap=exactmap memmap=1G@1G" will
make kernel use the memory from 1GB to 2GB only.
Signed-off-by: NPeng Liu <liupeng256@huawei.com>
Reviewed-by: NKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

Documentation/admin-guide/kernel-parameters.txt

@@ -2794,8 +2794,8 @@
 			option.
 			See Documentation/admin-guide/mm/memory-hotplug.rst.
 
-	memmap=exactmap	[KNL,X86] Enable setting of an exact
-			E820 memory map, as specified by the user.
+	memmap=exactmap	[KNL,X86,ARM64] Enable setting of an exact
+			E820 and ARM64 memory map, as specified by the user.
 			Such memmap=exactmap lines can be constructed based on
 			BIOS output or other requirements. See the memmap=nn@ss
 			option description.
@@ -2806,7 +2806,8 @@
 			If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
 			which limits max address to nn[KMG].
 			Multiple different regions can be specified,
-			comma delimited.
+			comma delimited, example as follows is not supported to
+			ARM64.
 			Example:
 				memmap=100M@2G,100M#3G,1G!1024G
 
@@ -2817,6 +2818,8 @@
 	memmap=nn[KMG]$ss[KMG]
 			[KNL,ACPI] Mark specific memory as reserved.
 			Region of memory to be reserved is from ss to ss+nn.
+			For ARM64, reserved memory must be in the range of
+			existed memory.
 			Example: Exclude memory from 0x18690000-0x1869ffff
 			         memmap=64K$0x18690000
 			         or

arch/arm64/mm/init.c

@@ -404,6 +404,65 @@ static int __init reserve_park_mem(void)
 }
 #endif
 
+static int need_remove_real_memblock __initdata;
+
+static int __init parse_memmap_one(char *p)
+{
+	char *oldp;
+	u64 start_at, mem_size;
+
+	if (!p)
+		return -EINVAL;
+
+	if (!strncmp(p, "exactmap", 8)) {
+		need_remove_real_memblock = 1;
+		return -EINVAL;
+	}
+
+	oldp = p;
+	mem_size = memparse(p, &p);
+	if (p == oldp)
+		return -EINVAL;
+
+	if (!mem_size)
+		return -EINVAL;
+
+	if (*p == '@') {
+		start_at = memparse(p + 1, &p);
+		/*
+		 * use the exactmap defined by nn[KMG]@ss[KMG], remove
+		 * memblock populated by DT etc.
+		 */
+		if (need_remove_real_memblock) {
+			need_remove_real_memblock = 0;
+			memblock_remove(0, ULLONG_MAX);
+		}
+		memblock_add(start_at, mem_size);
+	} else if (*p == '$') {
+		start_at = memparse(p + 1, &p);
+		memblock_reserve(start_at, mem_size);
+	} else
+		pr_info("Unrecognized memmap option, please check the parameter.\n");
+
+	return *p == '\0' ? 0 : -EINVAL;
+}
+
+static int __init parse_memmap_opt(char *str)
+{
+	while (str) {
+		char *k = strchr(str, ',');
+
+		if (k)
+			*k++ = 0;
+
+		parse_memmap_one(str);
+		str = k;
+	}
+
+	return 0;
+}
+early_param("memmap", parse_memmap_opt);
+
 void __init arm64_memblock_init(void)
 {
 	const s64 linear_region_size = BIT(vabits_actual - 1);