LoongArch: Add kdump support

This patch adds support for kdump. In kdump case the normal kernel will
reserve a region for the crash kernel and jump there on panic.

Arch-specific functions are added to allow for implementing a crash dump
file interface, /proc/vmcore, which can be viewed as a ELF file.

A user-space tool, such as kexec-tools, is responsible for allocating a
separate region for the core's ELF header within the crash kdump kernel
memory and filling it in when executing kexec_load().

Then, its location will be advertised to the crash dump kernel via a
command line argument "elfcorehdr=", and the crash dump kernel will
preserve this region for later use with arch_reserve_vmcore() at boot
time.

At the same time, the crash kdump kernel is also limited within the
"crashkernel" area via a command line argument "mem=", so as not to
destroy the original kernel dump data.

In the crash dump kernel environment, /proc/vmcore is used to access the
primary kernel's memory with copy_oldmem_page().

I tested kdump on LoongArch machines (Loongson-3A5000) and it works as
expected (suggested crashkernel parameter is "crashkernel=512M@2560M"),
you may test it by triggering a crash through /proc/sysrq-trigger:

 $ sudo kexec -p /boot/vmlinux-kdump --reuse-cmdline --append="nr_cpus=1"
 # echo c > /proc/sysrq-trigger

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

1 files changed, 74 insertions, 0 deletions

diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
index 05af1102fee7..837111292ec6 100644
--- a/arch/loongarch/kernel/setup.c
+++ b/arch/loongarch/kernel/setup.c
@@ -19,6 +19,8 @@
 #include <linux/memblock.h>
 #include <linux/initrd.h>
 #include <linux/ioport.h>
+#include <linux/kexec.h>
+#include <linux/crash_dump.h>
 #include <linux/root_dev.h>
 #include <linux/console.h>
 #include <linux/pfn.h>
@@ -185,8 +187,70 @@ static int __init early_parse_mem(char *p)
 }
 early_param("mem", early_parse_mem);
 
+static void __init arch_reserve_vmcore(void)
+{
+#ifdef CONFIG_PROC_VMCORE
+	u64 i;
+	phys_addr_t start, end;
+
+	if (!is_kdump_kernel())
+		return;
+
+	if (!elfcorehdr_size) {
+		for_each_mem_range(i, &start, &end) {
+			if (elfcorehdr_addr >= start && elfcorehdr_addr < end) {
+				/*
+				 * Reserve from the elf core header to the end of
+				 * the memory segment, that should all be kdump
+				 * reserved memory.
+				 */
+				elfcorehdr_size = end - elfcorehdr_addr;
+				break;
+			}
+		}
+	}
+
+	if (memblock_is_region_reserved(elfcorehdr_addr, elfcorehdr_size)) {
+		pr_warn("elfcorehdr is overlapped\n");
+		return;
+	}
+
+	memblock_reserve(elfcorehdr_addr, elfcorehdr_size);
+
+	pr_info("Reserving %llu KiB of memory at 0x%llx for elfcorehdr\n",
+		elfcorehdr_size >> 10, elfcorehdr_addr);
+#endif
+}
+
+static void __init arch_parse_crashkernel(void)
+{
+#ifdef CONFIG_KEXEC
+	int ret;
+	unsigned long long start;
+	unsigned long long total_mem;
+	unsigned long long crash_base, crash_size;
+
+	total_mem = memblock_phys_mem_size();
+	ret = parse_crashkernel(boot_command_line, total_mem, &crash_size, &crash_base);
+	if (ret < 0 || crash_size <= 0)
+		return;
+
+	start = memblock_phys_alloc_range(crash_size, 1, crash_base, crash_base + crash_size);
+	if (start != crash_base) {
+		pr_warn("Invalid memory region reserved for crash kernel\n");
+		return;
+	}
+
+	crashk_res.start = crash_base;
+	crashk_res.end	 = crash_base + crash_size - 1;
+#endif
+}
+
 void __init platform_init(void)
 {
+	arch_reserve_vmcore();
+	arch_parse_crashkernel();
+
 #ifdef CONFIG_ACPI_TABLE_UPGRADE
 	acpi_table_upgrade();
 #endif
@@ -289,6 +353,15 @@ 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 reserve_memblock_reserved_regions(void)
@@ -350,6 +423,7 @@ void __init setup_arch(char **cmdline_p)
 	memblock_init();
 	pagetable_init();
 	parse_early_param();
+	reserve_initrd_mem();
 
 	platform_init();
 	arch_mem_init(cmdline_p);