LoongArch: Use generic interface to support crashkernel=X,[high,low]

LoongArch already supports two crashkernel regions in kexec-tools, so we
can directly use the common interface to support crashkernel=X,[high,low]
after commit 0ab97169aa0517079b ("crash_core: add generic function to do
reservation").

With the help of newly changed function parse_crashkernel() and generic
reserve_crashkernel_generic(), crashkernel reservation can be simplified
by steps:

1) Add a new header file <asm/crash_core.h>, then define CRASH_ALIGN,
   CRASH_ADDR_LOW_MAX and CRASH_ADDR_HIGH_MAX and in <asm/crash_core.h>;

2) Add arch_reserve_crashkernel() to call parse_crashkernel() and
   reserve_crashkernel_generic();

3) Add ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION Kconfig in
   arch/loongarch/Kconfig.

One can reserve the crash kernel from high memory above DMA zone range
by explicitly passing "crashkernel=X,high"; or reserve a memory range
below 4G with "crashkernel=X,low". Besides, there are few rules need to
take notice:

1) "crashkernel=X,[high,low]" will be ignored if "crashkernel=size" is
   specified.
2) "crashkernel=X,low" is valid only when "crashkernel=X,high" is passed
   and there is enough memory to be allocated under 4G.
3) When allocating crashkernel above 4G and no "crashkernel=X,low" is
   specified, a 128M low memory will be allocated automatically for
   swiotlb bounce buffer.
See Documentation/admin-guide/kernel-parameters.txt for more information.

Following test cases have been performed as expected:
1) crashkernel=256M                          //low=256M
2) crashkernel=1G                            //low=1G
3) crashkernel=4G                            //high=4G, low=128M(default)
4) crashkernel=4G crashkernel=256M,high      //high=4G, low=128M(default), high is ignored
5) crashkernel=4G crashkernel=256M,low       //high=4G, low=128M(default), low is ignored
6) crashkernel=4G,high                       //high=4G, low=128M(default)
7) crashkernel=256M,low                      //low=0M, invalid
8) crashkernel=4G,high crashkernel=256M,low  //high=4G, low=256M
9) crashkernel=4G,high crashkernel=4G,low    //high=0M, low=0M, invalid
10) crashkernel=512M@2560M                   //low=512M
11) crashkernel=1G,high crashkernel=0M,low   //high=1G, low=0M

Recommended usage in general:
1) In the case of small memory: crashkernel=512M
2) In the case of large memory: crashkernel=1024M,high crashkernel=128M,low

Signed-off-by: Youling Tang <tangyouling@kylinos.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

1 files changed, 10 insertions, 34 deletions

diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
index 15d366b8407c..edf2bba80130 100644
--- a/arch/loongarch/kernel/setup.c
+++ b/arch/loongarch/kernel/setup.c
@@ -252,38 +252,23 @@ static void __init arch_reserve_vmcore(void)
 #endif
 }
 
-/* 2MB alignment for crash kernel regions */
-#define CRASH_ALIGN	SZ_2M
-#define CRASH_ADDR_MAX	SZ_4G
-
-static void __init arch_parse_crashkernel(void)
+static void __init arch_reserve_crashkernel(void)
 {
-#ifdef CONFIG_KEXEC
 	int ret;
-	unsigned long long total_mem;
+	unsigned long long low_size = 0;
 	unsigned long long crash_base, crash_size;
+	char *cmdline = boot_command_line;
+	bool high = false;
 
-	total_mem = memblock_phys_mem_size();
-	ret = parse_crashkernel(boot_command_line, total_mem,
-				&crash_size, &crash_base,
-				NULL, NULL);
-	if (ret < 0 || crash_size <= 0)
+	if (!IS_ENABLED(CONFIG_KEXEC_CORE))
 		return;
 
-	if (crash_base <= 0) {
-		crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN, CRASH_ALIGN, CRASH_ADDR_MAX);
-		if (!crash_base) {
-			pr_warn("crashkernel reservation failed - No suitable area found.\n");
-			return;
-		}
-	} else if (!memblock_phys_alloc_range(crash_size, CRASH_ALIGN, crash_base, crash_base + crash_size)) {
-		pr_warn("Invalid memory region reserved for crash kernel\n");
+	ret = parse_crashkernel(cmdline, memblock_phys_mem_size(),
+				&crash_size, &crash_base, &low_size, &high);
+	if (ret)
 		return;
-	}
 
-	crashk_res.start = crash_base;
-	crashk_res.end	 = crash_base + crash_size - 1;
-#endif
+	reserve_crashkernel_generic(cmdline, crash_size, crash_base, low_size, high);
 }
 
 static void __init fdt_setup(void)
@@ -363,7 +348,7 @@ out:
 void __init platform_init(void)
 {
 	arch_reserve_vmcore();
-	arch_parse_crashkernel();
+	arch_reserve_crashkernel();
 
 #ifdef CONFIG_ACPI_TABLE_UPGRADE
 	acpi_table_upgrade();
@@ -473,15 +458,6 @@ static void __init resource_init(void)
 		request_resource(res, &data_resource);
 		request_resource(res, &bss_resource);
 	}
-
-#ifdef CONFIG_KEXEC
-	if (crashk_res.start < crashk_res.end) {
-		insert_resource(&iomem_resource, &crashk_res);
-		pr_info("Reserving %ldMB of memory at %ldMB for crashkernel\n",
-			(unsigned long)((crashk_res.end - crashk_res.start + 1) >> 20),
-			(unsigned long)(crashk_res.start  >> 20));
-	}
-#endif
 }
 
 static int __init add_legacy_isa_io(struct fwnode_handle *fwnode,