[PATCH 1/7] LoongArch: Add KHO basic support

[George Guo <dongtai.guo@linux.dev>]

From: George Guo <guodongtai@kylinos.cn>

Enable Kexec Handover on LoongArch64:

- Kconfig: select ARCH_SUPPORTS_KEXEC_HANDOVER for 64BIT
- machine_kexec_file: add cmdline_add_kho() to pass the KHO FDT and
  scratch buffer addresses to the next kernel via the "kho_handover="
  command-line parameter
- setup: parse "kho_handover=" early and call kho_populate() to hand
  memory regions to the KHO core

Co-developed-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: George Guo <guodongtai@kylinos.cn>
---
 arch/loongarch/Kconfig                     |  3 +++
 arch/loongarch/kernel/machine_kexec_file.c | 22 ++++++++++++++++++
 arch/loongarch/kernel/setup.c              | 27 ++++++++++++++++++++++
 3 files changed, 52 insertions(+)

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 606597da46b8..d494418545f5 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -684,6 +684,9 @@ config ARCH_SUPPORTS_KEXEC
 config ARCH_SUPPORTS_KEXEC_FILE
 	def_bool 64BIT
 
+config ARCH_SUPPORTS_KEXEC_HANDOVER
+	def_bool 64BIT
+
 config ARCH_SELECTS_KEXEC_FILE
 	def_bool 64BIT
 	depends on KEXEC_FILE
diff --git a/arch/loongarch/kernel/machine_kexec_file.c b/arch/loongarch/kernel/machine_kexec_file.c
index 5584b798ba46..ddf4d0e0e7fd 100644
--- a/arch/loongarch/kernel/machine_kexec_file.c
+++ b/arch/loongarch/kernel/machine_kexec_file.c
@@ -55,6 +55,24 @@ static void cmdline_add_initrd(struct kimage *image, unsigned long *cmdline_tmpl
 	*cmdline_tmplen += initrd_strlen;
 }
 
+#ifdef CONFIG_KEXEC_HANDOVER
+/* Add "kho_handover=<fdt_size>@<fdt_addr>,<scratch_size>@<scratch_addr>" to cmdline. */
+static void cmdline_add_kho(struct kimage *image, unsigned long *cmdline_tmplen,
+			    char *modified_cmdline)
+{
+	int n;
+
+	if (!image->kho.fdt || !image->kho.scratch)
+		return;
+
+	n = sprintf(modified_cmdline + *cmdline_tmplen,
+	    "kho_handover=0x%llx@0x%llx,0x%lx@0x%llx ",
+	    (u64)PAGE_SIZE,               image->kho.fdt,
+	    image->kho.scratch->bufsz,    (u64)image->kho.scratch->mem);
+	*cmdline_tmplen += n;
+}
+#endif
+
 #ifdef CONFIG_CRASH_DUMP
 
 static int prepare_elf_headers(void **addr, unsigned long *sz)
@@ -220,6 +238,10 @@ int load_other_segments(struct kimage *image,
 		cmdline_add_initrd(image, &cmdline_tmplen, modified_cmdline, initrd_load_addr);
 	}
 
+#ifdef CONFIG_KEXEC_HANDOVER
+	cmdline_add_kho(image, &cmdline_tmplen, modified_cmdline);
+#endif
+
 	if (cmdline_len + cmdline_tmplen > COMMAND_LINE_SIZE) {
 		pr_err("Appending command line exceeds COMMAND_LINE_SIZE\n");
 		ret = -EINVAL;
diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
index 839b23edee87..5934ba6f13e3 100644
--- a/arch/loongarch/kernel/setup.c
+++ b/arch/loongarch/kernel/setup.c
@@ -48,6 +48,7 @@
 #include <asm/setup.h>
 #include <asm/time.h>
 #include <asm/unwind.h>
+#include <linux/kexec_handover.h>
 
 #define SMBIOS_BIOSSIZE_OFFSET		0x09
 #define SMBIOS_BIOSEXTERN_OFFSET	0x13
@@ -227,6 +228,32 @@ static int __init early_parse_mem(char *p)
 }
 early_param("mem", early_parse_mem);
 
+#ifdef CONFIG_KEXEC_HANDOVER
+static int __init early_parse_kho(char *p)
+{
+	phys_addr_t fdt_addr, scratch_addr;
+	u64 fdt_size, scratch_size;
+
+	if (!p)
+		return -EINVAL;
+
+	fdt_size = memparse(p, &p);
+	if (*p++ != '@')
+		return -EINVAL;
+	fdt_addr = memparse(p, &p);
+	if (*p++ != ',')
+		return -EINVAL;
+	scratch_size = memparse(p, &p);
+	if (*p++ != '@')
+		return -EINVAL;
+	scratch_addr = memparse(p, &p);
+
+	kho_populate(fdt_addr, fdt_size, scratch_addr, scratch_size);
+	return 0;
+}
+early_param("kho_handover", early_parse_kho);
+#endif
+
 static void __init arch_reserve_vmcore(void)
 {
 #ifdef CONFIG_PROC_VMCORE
-- 
2.25.1