[v1] LoongArch: Add kexec/kdump support

[PATCH 1/3] LoongArch: Add kexec support

Posted by Youling Tang 3 years, 7 months ago

Add three new files, kexec.h, machine_kexec.c and relocate_kernel.S to the
LoongArch architecture that add support for the kexec re-boot mechanis
(CONFIG_KEXEC) on LoongArch platforms.

Supports loading vmlinux (vmlinux.elf) in ELF format and vmlinux.efi in
PE format.

I tested this on  LoongArch 3A5000 machine and works as expected,

 $ sudo kexec -l /boot/vmlinux.efi --reuse-cmdline
 $ sudo kexec -e

Signed-off-by: Youling Tang <tangyouling@loongson.cn>
---
 arch/loongarch/Kconfig                  |  11 ++
 arch/loongarch/include/asm/kexec.h      |  58 ++++++++
 arch/loongarch/kernel/Makefile          |   2 +
 arch/loongarch/kernel/head.S            |   7 +-
 arch/loongarch/kernel/machine_kexec.c   | 178 ++++++++++++++++++++++++
 arch/loongarch/kernel/relocate_kernel.S | 125 +++++++++++++++++
 6 files changed, 380 insertions(+), 1 deletion(-)
 create mode 100644 arch/loongarch/include/asm/kexec.h
 create mode 100644 arch/loongarch/kernel/machine_kexec.c
 create mode 100644 arch/loongarch/kernel/relocate_kernel.S

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 45364cffc793..903c82fa958d 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -409,6 +409,17 @@ config FORCE_MAX_ZONEORDER
 	  The page size is not necessarily 4KB.  Keep this in mind
 	  when choosing a value for this option.
 
+config KEXEC
+	bool "Kexec system call"
+	select KEXEC_CORE
+	help
+	  kexec is a system call that implements the ability to shutdown your
+	  current kernel, and to start another kernel.  It is like a reboot
+	  but it is independent of the system firmware.   And like a reboot
+	  you can start any kernel with it, not just Linux.
+
+	  The name comes from the similarity to the exec system call.
+
 config SECCOMP
 	bool "Enable seccomp to safely compute untrusted bytecode"
 	depends on PROC_FS
diff --git a/arch/loongarch/include/asm/kexec.h b/arch/loongarch/include/asm/kexec.h
new file mode 100644
index 000000000000..5c9e7b5eccb8
--- /dev/null
+++ b/arch/loongarch/include/asm/kexec.h
@@ -0,0 +1,58 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * kexec.h for kexec
+ *
+ * Copyright (C) 2022 Loongson Technology Corporation Limited
+ */
+
+#ifndef _ASM_KEXEC_H
+#define _ASM_KEXEC_H
+
+#include <asm/stacktrace.h>
+#include <asm/page.h>
+
+/* Maximum physical address we can use pages from */
+#define KEXEC_SOURCE_MEMORY_LIMIT (-1UL)
+/* Maximum address we can reach in physical address mode */
+#define KEXEC_DESTINATION_MEMORY_LIMIT (-1UL)
+ /* Maximum address we can use for the control code buffer */
+#define KEXEC_CONTROL_MEMORY_LIMIT (-1UL)
+
+/* Reserve a page for the control code buffer */
+#define KEXEC_CONTROL_PAGE_SIZE PAGE_SIZE
+
+/* The native architecture */
+#define KEXEC_ARCH KEXEC_ARCH_LOONGARCH
+
+static inline void crash_setup_regs(struct pt_regs *newregs,
+				    struct pt_regs *oldregs)
+{
+	if (oldregs)
+		memcpy(newregs, oldregs, sizeof(*newregs));
+	else
+		prepare_frametrace(newregs);
+}
+
+#define ARCH_HAS_KIMAGE_ARCH
+
+struct kimage_arch {
+	unsigned long boot_flag;
+	unsigned long fdt_addr;
+};
+
+typedef void (*do_kexec_t)(unsigned long boot_flag,
+			   unsigned long fdt_addr,
+			   unsigned long first_ind_entry,
+			   unsigned long jump_addr);
+
+struct kimage;
+extern const unsigned char relocate_new_kernel[];
+extern const size_t relocate_new_kernel_size;
+
+#ifdef CONFIG_SMP
+extern atomic_t kexec_ready_to_reboot;
+extern const unsigned char kexec_smp_wait[];
+extern void kexec_reboot(void);
+#endif
+
+#endif /* !_ASM_KEXEC_H */
diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
index a213e994db68..20b64ac3f128 100644
--- a/arch/loongarch/kernel/Makefile
+++ b/arch/loongarch/kernel/Makefile
@@ -17,6 +17,8 @@ obj-$(CONFIG_CPU_HAS_FPU)	+= fpu.o
 obj-$(CONFIG_MODULES)		+= module.o module-sections.o
 obj-$(CONFIG_STACKTRACE)	+= stacktrace.o
 
+obj-$(CONFIG_KEXEC)             += machine_kexec.o relocate_kernel.o
+
 obj-$(CONFIG_PROC_FS)		+= proc.o
 
 obj-$(CONFIG_SMP)		+= smp.o
diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S
index 01bac62a6442..22bdf4928325 100644
--- a/arch/loongarch/kernel/head.S
+++ b/arch/loongarch/kernel/head.S
@@ -20,7 +20,12 @@
 
 _head:
 	.word	MZ_MAGIC		/* "MZ", MS-DOS header */
-	.org	0x3c			/* 0x04 ~ 0x3b reserved */
+	.org	0x8
+	.quad	0			/* Image load offset from start of RAM */
+	.dword	_end - _text		/* Effective size of kernel image */
+	.quad	0
+	.dword	kernel_entry		/* Kernel entry point */
+	.org	0x3c			/* 0x28 ~ 0x3b reserved */
 	.long	pe_header - _head	/* Offset to the PE header */
 
 pe_header:
diff --git a/arch/loongarch/kernel/machine_kexec.c b/arch/loongarch/kernel/machine_kexec.c
new file mode 100644
index 000000000000..4ffcd4cd9c8c
--- /dev/null
+++ b/arch/loongarch/kernel/machine_kexec.c
@@ -0,0 +1,178 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * machine_kexec.c for kexec
+ *
+ * Copyright (C) 2022 Loongson Technology Corporation Limited
+ */
+#include <linux/compiler.h>
+#include <linux/cpu.h>
+#include <linux/kexec.h>
+#include <linux/mm.h>
+#include <linux/delay.h>
+#include <linux/libfdt.h>
+#include <linux/of_fdt.h>
+
+#include <asm/bootinfo.h>
+#include <asm/cacheflush.h>
+#include <asm/page.h>
+
+/* 0x100000 ~ 0x200000 is safe */
+#define KEXEC_CTRL_CODE	TO_CACHE(0x100000UL)
+#define KEXEC_BLOB_ADDR	TO_CACHE(0x108000UL)
+
+static unsigned long reboot_code_buffer;
+#ifdef CONFIG_SMP
+void (*relocated_kexec_smp_wait)(void *);
+atomic_t kexec_ready_to_reboot = ATOMIC_INIT(0);
+#endif
+
+static unsigned long jump_addr;
+static unsigned long first_ind_entry;
+static unsigned long boot_flag;
+static unsigned long fdt_addr;
+
+static void kexec_image_info(const struct kimage *kimage)
+{
+	unsigned long i;
+
+	pr_debug("kexec kimage info:\n");
+	pr_debug("\ttype:        %d\n", kimage->type);
+	pr_debug("\tstart:       %lx\n", kimage->start);
+	pr_debug("\thead:        %lx\n", kimage->head);
+	pr_debug("\tnr_segments: %lu\n", kimage->nr_segments);
+
+	for (i = 0; i < kimage->nr_segments; i++) {
+		pr_debug("\t    segment[%lu]: %016lx - %016lx", i,
+			kimage->segment[i].mem,
+			kimage->segment[i].mem + kimage->segment[i].memsz);
+		pr_debug("\t\t0x%lx bytes, %lu pages\n",
+			(unsigned long)kimage->segment[i].memsz,
+			(unsigned long)kimage->segment[i].memsz /  PAGE_SIZE);
+	}
+}
+
+int machine_kexec_prepare(struct kimage *kimage)
+{
+	int i;
+	void *dtb = (void *)KEXEC_BLOB_ADDR;
+
+	kexec_image_info(kimage);
+
+	/* Find the Flattened Device Tree */
+	for (i = 0; i < kimage->nr_segments; i++) {
+		if (!fdt_check_header(kimage->segment[i].buf)) {
+			memcpy(dtb, kimage->segment[i].buf, SZ_64K);
+			kimage->arch.boot_flag = fw_arg0;
+			kimage->arch.fdt_addr = (unsigned long) dtb;
+			break;
+		}
+		continue;
+	}
+
+	/* kexec need a safe page to save reboot_code_buffer */
+	kimage->control_code_page = virt_to_page((void *)KEXEC_CTRL_CODE);
+
+	reboot_code_buffer =
+	  (unsigned long)page_address(kimage->control_code_page);
+	memcpy((void *)reboot_code_buffer, relocate_new_kernel,
+	       relocate_new_kernel_size);
+
+	/* All secondary cpus now may jump to kexec_smp_wait cycle */
+	relocated_kexec_smp_wait = reboot_code_buffer +
+		(void *)(kexec_smp_wait - relocate_new_kernel);
+
+	return 0;
+}
+
+void machine_kexec_cleanup(struct kimage *kimage)
+{
+}
+
+#ifdef CONFIG_SMP
+void kexec_reboot(void)
+{
+	do_kexec_t do_kexec = NULL;
+
+	/* All secondary cpus go to kexec_smp_wait */
+	if (smp_processor_id() > 0) {
+		relocated_kexec_smp_wait(NULL);
+		unreachable();
+	}
+
+	do_kexec = (void *)reboot_code_buffer;
+	do_kexec(boot_flag, fdt_addr, first_ind_entry, jump_addr);
+
+	unreachable();
+}
+
+static void kexec_shutdown_secondary(void *)
+{
+	local_irq_disable();
+	while (!atomic_read(&kexec_ready_to_reboot))
+		cpu_relax();
+
+	kexec_reboot();
+}
+
+void machine_crash_shutdown(struct pt_regs *regs)
+{
+}
+#endif
+
+void machine_shutdown(void)
+{
+	smp_call_function(kexec_shutdown_secondary, NULL, 0);
+}
+
+void machine_kexec(struct kimage *image)
+{
+	unsigned long entry;
+	unsigned long *ptr;
+	struct kimage_arch *internal = &image->arch;
+
+	boot_flag = internal->boot_flag;
+	fdt_addr = internal->fdt_addr;
+
+	jump_addr = (unsigned long)phys_to_virt(image->start);
+
+	first_ind_entry = (unsigned long)phys_to_virt(image->head & PAGE_MASK);
+
+	/*
+	 * The generic kexec code builds a page list with physical
+	 * addresses. they are directly accessible through XKPRANGE
+	 * hence the phys_to_virt() call.
+	 */
+	for (ptr = &image->head; (entry = *ptr) && !(entry & IND_DONE);
+	     ptr = (entry & IND_INDIRECTION) ?
+	       phys_to_virt(entry & PAGE_MASK) : ptr + 1) {
+		if (*ptr & IND_SOURCE || *ptr & IND_INDIRECTION ||
+		    *ptr & IND_DESTINATION)
+			*ptr = (unsigned long) phys_to_virt(*ptr);
+	}
+
+	/* Mark offline before disabling local irq. */
+	set_cpu_online(smp_processor_id(), false);
+
+	/* we do not want to be bothered. */
+	local_irq_disable();
+
+	pr_notice("Will call new kernel at %lx\n", jump_addr);
+	pr_notice("FDT image at %lx\n", fdt_addr);
+	pr_notice("Bye ...\n");
+
+	/* Make reboot code buffer available to the boot CPU. */
+	flush_cache_all();
+
+	atomic_set(&kexec_ready_to_reboot, 1);
+
+	/*
+	 * We know we were online, and there will be no incoming IPIs at
+	 * this point.
+	 */
+	set_cpu_online(smp_processor_id(), true);
+
+	/* Ensure remote CPUs observe that we're online before rebooting. */
+	smp_mb__after_atomic();
+
+	kexec_reboot();
+}
diff --git a/arch/loongarch/kernel/relocate_kernel.S b/arch/loongarch/kernel/relocate_kernel.S
new file mode 100644
index 000000000000..d1f242f74ea8
--- /dev/null
+++ b/arch/loongarch/kernel/relocate_kernel.S
@@ -0,0 +1,125 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * relocate_kernel.S for kexec
+ *
+ * Copyright (C) 2022 Loongson Technology Corporation Limited
+ */
+
+#include <linux/kexec.h>
+
+#include <asm/asm.h>
+#include <asm/asmmacro.h>
+#include <asm/regdef.h>
+#include <asm/loongarch.h>
+#include <asm/stackframe.h>
+#include <asm/addrspace.h>
+
+#define IPI_REG_BASE 0x1fe01000
+
+SYM_CODE_START(relocate_new_kernel)
+	/*
+	 * s0: Boot flag passed to the new kernel
+	 * s1: Virt address of the FDT image
+	 * s2: Pointer to the current entry
+	 * s3: Virt address to jump to after relocation
+	 */
+	move		s0, a0
+	move		s1, a1
+	move		s2, a2
+	move		s3, a3
+
+process_entry:
+	PTR_L		s4, s2, 0
+	PTR_ADDI	s2, s2, SZREG
+
+	/* destination page */
+	andi		s5, s4, IND_DESTINATION
+	beqz		s5, 1f
+	li.w		t0, ~0x1
+	and		s6, s4, t0	/* store destination addr in s6 */
+	b		process_entry
+
+1:
+	/* indirection page, update s2	*/
+	andi		s5, s4, IND_INDIRECTION
+	beqz		s5, 1f
+	li.w		t0, ~0x2
+	and		s2, s4, t0
+	b		process_entry
+
+1:
+	/* done page */
+	andi		s5, s4, IND_DONE
+	beqz		s5, 1f
+	b		done
+1:
+	/* source page */
+	andi		s5, s4, IND_SOURCE
+	beqz		s5, process_entry
+	li.w		t0, ~0x8
+	and		s4, s4, t0
+	li.w		s8, (1 << _PAGE_SHIFT) / SZREG
+
+copy_word:
+	/* copy page word by word */
+	REG_L		s7, s4, 0
+	REG_S		s7, s6, 0
+	PTR_ADDI	s6, s6, SZREG
+	PTR_ADDI	s4, s4, SZREG
+	LONG_ADDI	s8, s8, -1
+	beqz		s8, process_entry
+	b		copy_word
+	b		process_entry
+
+done:
+	dbar		0
+
+	move		a0, s0
+	move		a1, s1
+	/* jump to the new kernel */
+	jr		s3
+SYM_CODE_END(relocate_new_kernel)
+
+#ifdef CONFIG_SMP
+/*
+ * Other CPUs should wait until code is relocated and
+ * then start at entry (?) point.
+ */
+SYM_CODE_START(kexec_smp_wait)
+	li.d		t0, IPI_REG_BASE
+	li.d		t1, UNCACHE_BASE
+	or		t0, t0, t1
+
+	/*
+	 * s1:initfn
+	 * t0:base t1:cpuid t2:node t3:core t4:count
+	 */
+	csrrd		t1, LOONGARCH_CSR_CPUID
+	andi		t1, t1, CSR_CPUID_COREID
+	andi		t3, t1, 0x3
+	slli.w		t3, t3, 8              /* get core id */
+	or		t0, t0, t3
+	andi		t2, t1, 0x3c
+	slli.d		t2, t2, 42             /* get node id */
+	or		t0, t0, t2
+
+1:	li.w		t4, 0x100              /* wait for init loop */
+2:	addi.w		t4, t4, -1             /* limit mailbox access */
+	bnez		t4, 2b
+	ld.w		s1, t0, 0x20           /* check PC as an indicator */
+	beqz		s1, 1b
+	ld.d		s1, t0, 0x20           /* get PC via mailbox */
+	ld.d		sp, t0, 0x28           /* get SP via mailbox */
+	ld.d		tp, t0, 0x30           /* get TP via mailbox */
+
+	li.d		t0, CACHE_BASE
+	or		s1, s1, t0
+	jr		s1                     /* jump to initial PC */
+SYM_CODE_END(kexec_smp_wait)
+#endif
+
+relocate_new_kernel_end:
+
+SYM_DATA_START(relocate_new_kernel_size)
+	PTR		relocate_new_kernel_end - relocate_new_kernel
+SYM_DATA_END(relocate_new_kernel_size)
-- 
2.36.0

Re: [PATCH 1/3] LoongArch: Add kexec support

Posted by Youling Tang 3 years, 7 months ago


On 08/29/2022 12:37 PM, Youling Tang wrote:
> Add three new files, kexec.h, machine_kexec.c and relocate_kernel.S to the
> LoongArch architecture that add support for the kexec re-boot mechanis
> (CONFIG_KEXEC) on LoongArch platforms.
>
> Supports loading vmlinux (vmlinux.elf) in ELF format and vmlinux.efi in
> PE format.
>
> I tested this on  LoongArch 3A5000 machine and works as expected,
>
>  $ sudo kexec -l /boot/vmlinux.efi --reuse-cmdline
>  $ sudo kexec -e
>
> Signed-off-by: Youling Tang <tangyouling@loongson.cn>
> ---
>  arch/loongarch/Kconfig                  |  11 ++
>  arch/loongarch/include/asm/kexec.h      |  58 ++++++++
>  arch/loongarch/kernel/Makefile          |   2 +
>  arch/loongarch/kernel/head.S            |   7 +-
>  arch/loongarch/kernel/machine_kexec.c   | 178 ++++++++++++++++++++++++
>  arch/loongarch/kernel/relocate_kernel.S | 125 +++++++++++++++++
>  6 files changed, 380 insertions(+), 1 deletion(-)
>  create mode 100644 arch/loongarch/include/asm/kexec.h
>  create mode 100644 arch/loongarch/kernel/machine_kexec.c
>  create mode 100644 arch/loongarch/kernel/relocate_kernel.S
>
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index 45364cffc793..903c82fa958d 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -409,6 +409,17 @@ config FORCE_MAX_ZONEORDER
>  	  The page size is not necessarily 4KB.  Keep this in mind
>  	  when choosing a value for this option.
>
> +config KEXEC
> +	bool "Kexec system call"
> +	select KEXEC_CORE
> +	help
> +	  kexec is a system call that implements the ability to shutdown your
> +	  current kernel, and to start another kernel.  It is like a reboot
> +	  but it is independent of the system firmware.   And like a reboot
> +	  you can start any kernel with it, not just Linux.
> +
> +	  The name comes from the similarity to the exec system call.
> +
>  config SECCOMP
>  	bool "Enable seccomp to safely compute untrusted bytecode"
>  	depends on PROC_FS
> diff --git a/arch/loongarch/include/asm/kexec.h b/arch/loongarch/include/asm/kexec.h
> new file mode 100644
> index 000000000000..5c9e7b5eccb8
> --- /dev/null
> +++ b/arch/loongarch/include/asm/kexec.h
> @@ -0,0 +1,58 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * kexec.h for kexec
> + *
> + * Copyright (C) 2022 Loongson Technology Corporation Limited
> + */
> +
> +#ifndef _ASM_KEXEC_H
> +#define _ASM_KEXEC_H
> +
> +#include <asm/stacktrace.h>
> +#include <asm/page.h>
> +
> +/* Maximum physical address we can use pages from */
> +#define KEXEC_SOURCE_MEMORY_LIMIT (-1UL)
> +/* Maximum address we can reach in physical address mode */
> +#define KEXEC_DESTINATION_MEMORY_LIMIT (-1UL)
> + /* Maximum address we can use for the control code buffer */
> +#define KEXEC_CONTROL_MEMORY_LIMIT (-1UL)
> +
> +/* Reserve a page for the control code buffer */
> +#define KEXEC_CONTROL_PAGE_SIZE PAGE_SIZE
> +
> +/* The native architecture */
> +#define KEXEC_ARCH KEXEC_ARCH_LOONGARCH
> +
> +static inline void crash_setup_regs(struct pt_regs *newregs,
> +				    struct pt_regs *oldregs)
> +{
> +	if (oldregs)
> +		memcpy(newregs, oldregs, sizeof(*newregs));
> +	else
> +		prepare_frametrace(newregs);
> +}
> +
> +#define ARCH_HAS_KIMAGE_ARCH
> +
> +struct kimage_arch {
> +	unsigned long boot_flag;
> +	unsigned long fdt_addr;
> +};
> +
> +typedef void (*do_kexec_t)(unsigned long boot_flag,
> +			   unsigned long fdt_addr,
> +			   unsigned long first_ind_entry,
> +			   unsigned long jump_addr);
> +
> +struct kimage;
> +extern const unsigned char relocate_new_kernel[];
> +extern const size_t relocate_new_kernel_size;
> +
> +#ifdef CONFIG_SMP
> +extern atomic_t kexec_ready_to_reboot;
> +extern const unsigned char kexec_smp_wait[];
> +extern void kexec_reboot(void);
> +#endif
> +
> +#endif /* !_ASM_KEXEC_H */
> diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
> index a213e994db68..20b64ac3f128 100644
> --- a/arch/loongarch/kernel/Makefile
> +++ b/arch/loongarch/kernel/Makefile
> @@ -17,6 +17,8 @@ obj-$(CONFIG_CPU_HAS_FPU)	+= fpu.o
>  obj-$(CONFIG_MODULES)		+= module.o module-sections.o
>  obj-$(CONFIG_STACKTRACE)	+= stacktrace.o
>
> +obj-$(CONFIG_KEXEC)             += machine_kexec.o relocate_kernel.o
> +
>  obj-$(CONFIG_PROC_FS)		+= proc.o
>
>  obj-$(CONFIG_SMP)		+= smp.o
> diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S
> index 01bac62a6442..22bdf4928325 100644
> --- a/arch/loongarch/kernel/head.S
> +++ b/arch/loongarch/kernel/head.S
> @@ -20,7 +20,12 @@
>
>  _head:
>  	.word	MZ_MAGIC		/* "MZ", MS-DOS header */
> -	.org	0x3c			/* 0x04 ~ 0x3b reserved */
> +	.org	0x8
> +	.quad	0			/* Image load offset from start of RAM */
> +	.dword	_end - _text		/* Effective size of kernel image */
> +	.quad	0
> +	.dword	kernel_entry		/* Kernel entry point */
> +	.org	0x3c			/* 0x28 ~ 0x3b reserved */
>  	.long	pe_header - _head	/* Offset to the PE header */
>
>  pe_header:
> diff --git a/arch/loongarch/kernel/machine_kexec.c b/arch/loongarch/kernel/machine_kexec.c
> new file mode 100644
> index 000000000000..4ffcd4cd9c8c
> --- /dev/null
> +++ b/arch/loongarch/kernel/machine_kexec.c
> @@ -0,0 +1,178 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * machine_kexec.c for kexec
> + *
> + * Copyright (C) 2022 Loongson Technology Corporation Limited
> + */
> +#include <linux/compiler.h>
> +#include <linux/cpu.h>
> +#include <linux/kexec.h>
> +#include <linux/mm.h>
> +#include <linux/delay.h>
> +#include <linux/libfdt.h>
> +#include <linux/of_fdt.h>
> +
> +#include <asm/bootinfo.h>
> +#include <asm/cacheflush.h>
> +#include <asm/page.h>
> +
> +/* 0x100000 ~ 0x200000 is safe */
> +#define KEXEC_CTRL_CODE	TO_CACHE(0x100000UL)
> +#define KEXEC_BLOB_ADDR	TO_CACHE(0x108000UL)
> +
> +static unsigned long reboot_code_buffer;
> +#ifdef CONFIG_SMP
> +void (*relocated_kexec_smp_wait)(void *);
> +atomic_t kexec_ready_to_reboot = ATOMIC_INIT(0);
> +#endif
> +
> +static unsigned long jump_addr;
> +static unsigned long first_ind_entry;
> +static unsigned long boot_flag;
> +static unsigned long fdt_addr;
> +
> +static void kexec_image_info(const struct kimage *kimage)
> +{
> +	unsigned long i;
> +
> +	pr_debug("kexec kimage info:\n");
> +	pr_debug("\ttype:        %d\n", kimage->type);
> +	pr_debug("\tstart:       %lx\n", kimage->start);
> +	pr_debug("\thead:        %lx\n", kimage->head);
> +	pr_debug("\tnr_segments: %lu\n", kimage->nr_segments);
> +
> +	for (i = 0; i < kimage->nr_segments; i++) {
> +		pr_debug("\t    segment[%lu]: %016lx - %016lx", i,
> +			kimage->segment[i].mem,
> +			kimage->segment[i].mem + kimage->segment[i].memsz);
> +		pr_debug("\t\t0x%lx bytes, %lu pages\n",
> +			(unsigned long)kimage->segment[i].memsz,
> +			(unsigned long)kimage->segment[i].memsz /  PAGE_SIZE);
> +	}
> +}
> +
> +int machine_kexec_prepare(struct kimage *kimage)
> +{
> +	int i;
> +	void *dtb = (void *)KEXEC_BLOB_ADDR;
> +
> +	kexec_image_info(kimage);
> +
> +	/* Find the Flattened Device Tree */
> +	for (i = 0; i < kimage->nr_segments; i++) {
> +		if (!fdt_check_header(kimage->segment[i].buf)) {
> +			memcpy(dtb, kimage->segment[i].buf, SZ_64K);
> +			kimage->arch.boot_flag = fw_arg0;
> +			kimage->arch.fdt_addr = (unsigned long) dtb;
> +			break;
> +		}
> +		continue;
> +	}
> +
> +	/* kexec need a safe page to save reboot_code_buffer */
> +	kimage->control_code_page = virt_to_page((void *)KEXEC_CTRL_CODE);
> +
> +	reboot_code_buffer =
> +	  (unsigned long)page_address(kimage->control_code_page);
> +	memcpy((void *)reboot_code_buffer, relocate_new_kernel,
> +	       relocate_new_kernel_size);
> +
> +	/* All secondary cpus now may jump to kexec_smp_wait cycle */
> +	relocated_kexec_smp_wait = reboot_code_buffer +
> +		(void *)(kexec_smp_wait - relocate_new_kernel);
> +
> +	return 0;
> +}
> +
> +void machine_kexec_cleanup(struct kimage *kimage)
> +{
> +}
> +
> +#ifdef CONFIG_SMP
> +void kexec_reboot(void)
> +{
> +	do_kexec_t do_kexec = NULL;
> +
> +	/* All secondary cpus go to kexec_smp_wait */
> +	if (smp_processor_id() > 0) {
> +		relocated_kexec_smp_wait(NULL);
> +		unreachable();
> +	}
> +
> +	do_kexec = (void *)reboot_code_buffer;
> +	do_kexec(boot_flag, fdt_addr, first_ind_entry, jump_addr);
> +
> +	unreachable();
> +}

self-check,
kexec_reboot() is in! SMP needs to be used, modified as follows:

void kexec_reboot(void)
{
         do_kexec_t do_kexec = NULL;

#ifdef CONFIG_SMP
         /* All secondary cpus go to kexec_smp_wait */
         if (smp_processor_id() > 0) {
                 relocated_kexec_smp_wait(NULL);
                 unreachable();
         }
#endif

         do_kexec = (void *)reboot_code_buffer;
         do_kexec(boot_flag, fdt_addr, first_ind_entry, jump_addr);

         unreachable();
}

Youling

Re: [PATCH 1/3] LoongArch: Add kexec support

Posted by Jinyang He 3 years, 7 months ago

Hi, Youling,


On 08/29/2022 12:37 PM, Youling Tang wrote:
> Add three new files, kexec.h, machine_kexec.c and relocate_kernel.S to the
> LoongArch architecture that add support for the kexec re-boot mechanis
> (CONFIG_KEXEC) on LoongArch platforms.
>
> Supports loading vmlinux (vmlinux.elf) in ELF format and vmlinux.efi in
> PE format.
>
> I tested this on  LoongArch 3A5000 machine and works as expected,
>
>   $ sudo kexec -l /boot/vmlinux.efi --reuse-cmdline
>   $ sudo kexec -e
>
> Signed-off-by: Youling Tang <tangyouling@loongson.cn>
> ---
>   arch/loongarch/Kconfig                  |  11 ++
>   arch/loongarch/include/asm/kexec.h      |  58 ++++++++
>   arch/loongarch/kernel/Makefile          |   2 +
>   arch/loongarch/kernel/head.S            |   7 +-
>   arch/loongarch/kernel/machine_kexec.c   | 178 ++++++++++++++++++++++++
>   arch/loongarch/kernel/relocate_kernel.S | 125 +++++++++++++++++
>   6 files changed, 380 insertions(+), 1 deletion(-)
>   create mode 100644 arch/loongarch/include/asm/kexec.h
>   create mode 100644 arch/loongarch/kernel/machine_kexec.c
>   create mode 100644 arch/loongarch/kernel/relocate_kernel.S
>
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index 45364cffc793..903c82fa958d 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -409,6 +409,17 @@ config FORCE_MAX_ZONEORDER
>   	  The page size is not necessarily 4KB.  Keep this in mind
>   	  when choosing a value for this option.
>   
> +config KEXEC
> +	bool "Kexec system call"
> +	select KEXEC_CORE
> +	help
> +	  kexec is a system call that implements the ability to shutdown your
> +	  current kernel, and to start another kernel.  It is like a reboot
> +	  but it is independent of the system firmware.   And like a reboot
> +	  you can start any kernel with it, not just Linux.
> +
> +	  The name comes from the similarity to the exec system call.
> +
>   config SECCOMP
>   	bool "Enable seccomp to safely compute untrusted bytecode"
>   	depends on PROC_FS
> diff --git a/arch/loongarch/include/asm/kexec.h b/arch/loongarch/include/asm/kexec.h
> new file mode 100644
> index 000000000000..5c9e7b5eccb8
> --- /dev/null
> +++ b/arch/loongarch/include/asm/kexec.h
> @@ -0,0 +1,58 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * kexec.h for kexec
> + *
> + * Copyright (C) 2022 Loongson Technology Corporation Limited
> + */
> +
> +#ifndef _ASM_KEXEC_H
> +#define _ASM_KEXEC_H
> +
> +#include <asm/stacktrace.h>
> +#include <asm/page.h>
> +
> +/* Maximum physical address we can use pages from */
> +#define KEXEC_SOURCE_MEMORY_LIMIT (-1UL)
> +/* Maximum address we can reach in physical address mode */
> +#define KEXEC_DESTINATION_MEMORY_LIMIT (-1UL)
> + /* Maximum address we can use for the control code buffer */
> +#define KEXEC_CONTROL_MEMORY_LIMIT (-1UL)
> +
> +/* Reserve a page for the control code buffer */
> +#define KEXEC_CONTROL_PAGE_SIZE PAGE_SIZE
> +
> +/* The native architecture */
> +#define KEXEC_ARCH KEXEC_ARCH_LOONGARCH
> +
> +static inline void crash_setup_regs(struct pt_regs *newregs,
> +				    struct pt_regs *oldregs)
> +{
> +	if (oldregs)
> +		memcpy(newregs, oldregs, sizeof(*newregs));
> +	else
> +		prepare_frametrace(newregs);
> +}
> +
> +#define ARCH_HAS_KIMAGE_ARCH
> +
> +struct kimage_arch {
> +	unsigned long boot_flag;
> +	unsigned long fdt_addr;
> +};
> +
> +typedef void (*do_kexec_t)(unsigned long boot_flag,
> +			   unsigned long fdt_addr,
> +			   unsigned long first_ind_entry,
> +			   unsigned long jump_addr);
> +
> +struct kimage;
> +extern const unsigned char relocate_new_kernel[];
> +extern const size_t relocate_new_kernel_size;
> +
> +#ifdef CONFIG_SMP
> +extern atomic_t kexec_ready_to_reboot;
> +extern const unsigned char kexec_smp_wait[];
> +extern void kexec_reboot(void);
> +#endif
> +
> +#endif /* !_ASM_KEXEC_H */
> diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
> index a213e994db68..20b64ac3f128 100644
> --- a/arch/loongarch/kernel/Makefile
> +++ b/arch/loongarch/kernel/Makefile
> @@ -17,6 +17,8 @@ obj-$(CONFIG_CPU_HAS_FPU)	+= fpu.o
>   obj-$(CONFIG_MODULES)		+= module.o module-sections.o
>   obj-$(CONFIG_STACKTRACE)	+= stacktrace.o
>   
> +obj-$(CONFIG_KEXEC)             += machine_kexec.o relocate_kernel.o
> +
>   obj-$(CONFIG_PROC_FS)		+= proc.o
>   
>   obj-$(CONFIG_SMP)		+= smp.o
> diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S
> index 01bac62a6442..22bdf4928325 100644
> --- a/arch/loongarch/kernel/head.S
> +++ b/arch/loongarch/kernel/head.S
> @@ -20,7 +20,12 @@
>   
>   _head:
>   	.word	MZ_MAGIC		/* "MZ", MS-DOS header */
> -	.org	0x3c			/* 0x04 ~ 0x3b reserved */
> +	.org	0x8
> +	.quad	0			/* Image load offset from start of RAM */
> +	.dword	_end - _text		/* Effective size of kernel image */
> +	.quad	0
> +	.dword	kernel_entry		/* Kernel entry point */
> +	.org	0x3c			/* 0x28 ~ 0x3b reserved */
>   	.long	pe_header - _head	/* Offset to the PE header */
>   
>   pe_header:
> diff --git a/arch/loongarch/kernel/machine_kexec.c b/arch/loongarch/kernel/machine_kexec.c
> new file mode 100644
> index 000000000000..4ffcd4cd9c8c
> --- /dev/null
> +++ b/arch/loongarch/kernel/machine_kexec.c
> @@ -0,0 +1,178 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * machine_kexec.c for kexec
> + *
> + * Copyright (C) 2022 Loongson Technology Corporation Limited
> + */
> +#include <linux/compiler.h>
> +#include <linux/cpu.h>
> +#include <linux/kexec.h>
> +#include <linux/mm.h>
> +#include <linux/delay.h>
> +#include <linux/libfdt.h>
> +#include <linux/of_fdt.h>
> +
> +#include <asm/bootinfo.h>
> +#include <asm/cacheflush.h>
> +#include <asm/page.h>
> +
> +/* 0x100000 ~ 0x200000 is safe */
> +#define KEXEC_CTRL_CODE	TO_CACHE(0x100000UL)
> +#define KEXEC_BLOB_ADDR	TO_CACHE(0x108000UL)
> +
> +static unsigned long reboot_code_buffer;
> +#ifdef CONFIG_SMP
> +void (*relocated_kexec_smp_wait)(void *);
> +atomic_t kexec_ready_to_reboot = ATOMIC_INIT(0);
> +#endif
> +
> +static unsigned long jump_addr;
> +static unsigned long first_ind_entry;
> +static unsigned long boot_flag;
> +static unsigned long fdt_addr;
> +
> +static void kexec_image_info(const struct kimage *kimage)
> +{
> +	unsigned long i;
> +
> +	pr_debug("kexec kimage info:\n");
> +	pr_debug("\ttype:        %d\n", kimage->type);
> +	pr_debug("\tstart:       %lx\n", kimage->start);
> +	pr_debug("\thead:        %lx\n", kimage->head);
> +	pr_debug("\tnr_segments: %lu\n", kimage->nr_segments);
> +
> +	for (i = 0; i < kimage->nr_segments; i++) {
> +		pr_debug("\t    segment[%lu]: %016lx - %016lx", i,
> +			kimage->segment[i].mem,
> +			kimage->segment[i].mem + kimage->segment[i].memsz);
> +		pr_debug("\t\t0x%lx bytes, %lu pages\n",
> +			(unsigned long)kimage->segment[i].memsz,
> +			(unsigned long)kimage->segment[i].memsz /  PAGE_SIZE);
> +	}
> +}
> +
> +int machine_kexec_prepare(struct kimage *kimage)
> +{
> +	int i;
> +	void *dtb = (void *)KEXEC_BLOB_ADDR;
> +
> +	kexec_image_info(kimage);
> +
> +	/* Find the Flattened Device Tree */
> +	for (i = 0; i < kimage->nr_segments; i++) {
> +		if (!fdt_check_header(kimage->segment[i].buf)) {
> +			memcpy(dtb, kimage->segment[i].buf, SZ_64K);
> +			kimage->arch.boot_flag = fw_arg0;
> +			kimage->arch.fdt_addr = (unsigned long) dtb;
> +			break;
> +		}
> +		continue;
> +	}
> +
> +	/* kexec need a safe page to save reboot_code_buffer */
> +	kimage->control_code_page = virt_to_page((void *)KEXEC_CTRL_CODE);
> +
> +	reboot_code_buffer =
> +	  (unsigned long)page_address(kimage->control_code_page);
> +	memcpy((void *)reboot_code_buffer, relocate_new_kernel,
> +	       relocate_new_kernel_size);
It copys same content to KEXEC_CTRL_CODE each time, could we do this at 
boot time?

BTW, our system always keep the low-2MB no used, on mips-loongson or
LoongArch. Is that necessary on LoongArch? We cannot use parameter
'mem=YYM' normally but 'mem=YYM@2M' is ok. And the low-2MB is not
in virtual memory management, although we can get it in kernel.

In kexec/kdump process, we can follows kimage_alloc_control_pages().
When the boot cpu copy complete the second-kernels, all cpus can jump
to a kernel-entry-trampoline which is in kernel image. Then we don't
worry about the code can be destroyed. The kernel-entry-trampoline
get its cpuid, keep non-boot cpus do as kexec_smp_wait and let boot
cpu go kernel-entry. In this way we can drop the low-2MB IMO.

> +
> +	/* All secondary cpus now may jump to kexec_smp_wait cycle */
> +	relocated_kexec_smp_wait = reboot_code_buffer +
> +		(void *)(kexec_smp_wait - relocate_new_kernel);
> +
> +	return 0;
> +}
> +
> +void machine_kexec_cleanup(struct kimage *kimage)
> +{
> +}
> +
> +#ifdef CONFIG_SMP
> +void kexec_reboot(void)
> +{
> +	do_kexec_t do_kexec = NULL;
> +
> +	/* All secondary cpus go to kexec_smp_wait */
> +	if (smp_processor_id() > 0) {
> +		relocated_kexec_smp_wait(NULL);
> +		unreachable();
> +	}
> +
> +	do_kexec = (void *)reboot_code_buffer;
> +	do_kexec(boot_flag, fdt_addr, first_ind_entry, jump_addr);
> +
> +	unreachable();
> +}
> +
> +static void kexec_shutdown_secondary(void *)
> +{
> +	local_irq_disable();
> +	while (!atomic_read(&kexec_ready_to_reboot))
> +		cpu_relax();
> +
> +	kexec_reboot();
> +}
> +
> +void machine_crash_shutdown(struct pt_regs *regs)
> +{
> +}
> +#endif
> +
> +void machine_shutdown(void)
> +{
> +	smp_call_function(kexec_shutdown_secondary, NULL, 0);
> +}
> +
> +void machine_kexec(struct kimage *image)
> +{
> +	unsigned long entry;
> +	unsigned long *ptr;
> +	struct kimage_arch *internal = &image->arch;
> +
> +	boot_flag = internal->boot_flag;
> +	fdt_addr = internal->fdt_addr;
> +
> +	jump_addr = (unsigned long)phys_to_virt(image->start);
> +
> +	first_ind_entry = (unsigned long)phys_to_virt(image->head & PAGE_MASK);
> +
> +	/*
> +	 * The generic kexec code builds a page list with physical
> +	 * addresses. they are directly accessible through XKPRANGE
> +	 * hence the phys_to_virt() call.
> +	 */
> +	for (ptr = &image->head; (entry = *ptr) && !(entry & IND_DONE);
> +	     ptr = (entry & IND_INDIRECTION) ?
> +	       phys_to_virt(entry & PAGE_MASK) : ptr + 1) {
> +		if (*ptr & IND_SOURCE || *ptr & IND_INDIRECTION ||
> +		    *ptr & IND_DESTINATION)
> +			*ptr = (unsigned long) phys_to_virt(*ptr);
> +	}
> +
> +	/* Mark offline before disabling local irq. */
> +	set_cpu_online(smp_processor_id(), false);
> +
> +	/* we do not want to be bothered. */
> +	local_irq_disable();
> +
> +	pr_notice("Will call new kernel at %lx\n", jump_addr);
> +	pr_notice("FDT image at %lx\n", fdt_addr);
> +	pr_notice("Bye ...\n");
> +
> +	/* Make reboot code buffer available to the boot CPU. */
> +	flush_cache_all();
> +
> +	atomic_set(&kexec_ready_to_reboot, 1);
> +
> +	/*
> +	 * We know we were online, and there will be no incoming IPIs at
> +	 * this point.
> +	 */
> +	set_cpu_online(smp_processor_id(), true);
> +
> +	/* Ensure remote CPUs observe that we're online before rebooting. */
> +	smp_mb__after_atomic();
> +
> +	kexec_reboot();
> +}
> diff --git a/arch/loongarch/kernel/relocate_kernel.S b/arch/loongarch/kernel/relocate_kernel.S
> new file mode 100644
> index 000000000000..d1f242f74ea8
> --- /dev/null
> +++ b/arch/loongarch/kernel/relocate_kernel.S
> @@ -0,0 +1,125 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * relocate_kernel.S for kexec
> + *
> + * Copyright (C) 2022 Loongson Technology Corporation Limited
> + */
> +
> +#include <linux/kexec.h>
> +
> +#include <asm/asm.h>
> +#include <asm/asmmacro.h>
> +#include <asm/regdef.h>
> +#include <asm/loongarch.h>
> +#include <asm/stackframe.h>
> +#include <asm/addrspace.h>
> +
> +#define IPI_REG_BASE 0x1fe01000
> +
> +SYM_CODE_START(relocate_new_kernel)
> +	/*
> +	 * s0: Boot flag passed to the new kernel
> +	 * s1: Virt address of the FDT image
> +	 * s2: Pointer to the current entry
> +	 * s3: Virt address to jump to after relocation
> +	 */
> +	move		s0, a0
> +	move		s1, a1
> +	move		s2, a2
> +	move		s3, a3
> +
> +process_entry:
> +	PTR_L		s4, s2, 0
> +	PTR_ADDI	s2, s2, SZREG
> +
> +	/* destination page */
> +	andi		s5, s4, IND_DESTINATION
> +	beqz		s5, 1f
> +	li.w		t0, ~0x1
> +	and		s6, s4, t0	/* store destination addr in s6 */
> +	b		process_entry
> +
> +1:
> +	/* indirection page, update s2	*/
> +	andi		s5, s4, IND_INDIRECTION
> +	beqz		s5, 1f
> +	li.w		t0, ~0x2
> +	and		s2, s4, t0
> +	b		process_entry
> +
> +1:
> +	/* done page */
> +	andi		s5, s4, IND_DONE
> +	beqz		s5, 1f
> +	b		done
> +1:
> +	/* source page */
> +	andi		s5, s4, IND_SOURCE
> +	beqz		s5, process_entry
> +	li.w		t0, ~0x8
> +	and		s4, s4, t0
> +	li.w		s8, (1 << _PAGE_SHIFT) / SZREG
> +
> +copy_word:
> +	/* copy page word by word */
> +	REG_L		s7, s4, 0
> +	REG_S		s7, s6, 0
> +	PTR_ADDI	s6, s6, SZREG
> +	PTR_ADDI	s4, s4, SZREG
> +	LONG_ADDI	s8, s8, -1
> +	beqz		s8, process_entry
> +	b		copy_word
> +	b		process_entry
> +
> +done:
> +	dbar		0
ibar, too?
> +
> +	move		a0, s0
> +	move		a1, s1
> +	/* jump to the new kernel */
> +	jr		s3
> +SYM_CODE_END(relocate_new_kernel)
> +
> +#ifdef CONFIG_SMP
> +/*
> + * Other CPUs should wait until code is relocated and
> + * then start at entry (?) point.
> + */
> +SYM_CODE_START(kexec_smp_wait)
> +	li.d		t0, IPI_REG_BASE
> +	li.d		t1, UNCACHE_BASE
> +	or		t0, t0, t1
> +
> +	/*
> +	 * s1:initfn
> +	 * t0:base t1:cpuid t2:node t3:core t4:count
> +	 */
> +	csrrd		t1, LOONGARCH_CSR_CPUID
> +	andi		t1, t1, CSR_CPUID_COREID
> +	andi		t3, t1, 0x3
> +	slli.w		t3, t3, 8              /* get core id */
> +	or		t0, t0, t3
> +	andi		t2, t1, 0x3c
> +	slli.d		t2, t2, 42             /* get node id */
> +	or		t0, t0, t2
> +
> +1:	li.w		t4, 0x100              /* wait for init loop */
> +2:	addi.w		t4, t4, -1             /* limit mailbox access */
> +	bnez		t4, 2b
> +	ld.w		s1, t0, 0x20           /* check PC as an indicator */
Can we do this with iocsr*?

Thanks,
Jinyang
> +	beqz		s1, 1b
> +	ld.d		s1, t0, 0x20           /* get PC via mailbox */
> +	ld.d		sp, t0, 0x28           /* get SP via mailbox */
> +	ld.d		tp, t0, 0x30           /* get TP via mailbox */
> +
> +	li.d		t0, CACHE_BASE
> +	or		s1, s1, t0
> +	jr		s1                     /* jump to initial PC */
> +SYM_CODE_END(kexec_smp_wait)
> +#endif
> +
> +relocate_new_kernel_end:
> +
> +SYM_DATA_START(relocate_new_kernel_size)
> +	PTR		relocate_new_kernel_end - relocate_new_kernel
> +SYM_DATA_END(relocate_new_kernel_size)

Re: [PATCH 1/3] LoongArch: Add kexec support

Posted by Youling Tang 3 years, 7 months ago

Hi, Jinyang

On 08/30/2022 09:53 AM, Jinyang He wrote:
> Hi, Youling,
>
>
> On 08/29/2022 12:37 PM, Youling Tang wrote:
>> Add three new files, kexec.h, machine_kexec.c and relocate_kernel.S to
>> the
>> LoongArch architecture that add support for the kexec re-boot mechanis
>> (CONFIG_KEXEC) on LoongArch platforms.
>>
>> Supports loading vmlinux (vmlinux.elf) in ELF format and vmlinux.efi in
>> PE format.
>>
>> I tested this on  LoongArch 3A5000 machine and works as expected,
>>
>>   $ sudo kexec -l /boot/vmlinux.efi --reuse-cmdline
>>   $ sudo kexec -e
>>
>> Signed-off-by: Youling Tang <tangyouling@loongson.cn>
>> ---
>>   arch/loongarch/Kconfig                  |  11 ++
>>   arch/loongarch/include/asm/kexec.h      |  58 ++++++++
>>   arch/loongarch/kernel/Makefile          |   2 +
>>   arch/loongarch/kernel/head.S            |   7 +-
>>   arch/loongarch/kernel/machine_kexec.c   | 178 ++++++++++++++++++++++++
>>   arch/loongarch/kernel/relocate_kernel.S | 125 +++++++++++++++++
>>   6 files changed, 380 insertions(+), 1 deletion(-)
>>   create mode 100644 arch/loongarch/include/asm/kexec.h
>>   create mode 100644 arch/loongarch/kernel/machine_kexec.c
>>   create mode 100644 arch/loongarch/kernel/relocate_kernel.S
>>
>> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
>> index 45364cffc793..903c82fa958d 100644
>> --- a/arch/loongarch/Kconfig
>> +++ b/arch/loongarch/Kconfig
>> @@ -409,6 +409,17 @@ config FORCE_MAX_ZONEORDER
>>         The page size is not necessarily 4KB.  Keep this in mind
>>         when choosing a value for this option.
>>   +config KEXEC
>> +    bool "Kexec system call"
>> +    select KEXEC_CORE
>> +    help
>> +      kexec is a system call that implements the ability to shutdown
>> your
>> +      current kernel, and to start another kernel.  It is like a reboot
>> +      but it is independent of the system firmware.   And like a reboot
>> +      you can start any kernel with it, not just Linux.
>> +
>> +      The name comes from the similarity to the exec system call.
>> +
>>   config SECCOMP
>>       bool "Enable seccomp to safely compute untrusted bytecode"
>>       depends on PROC_FS
>> diff --git a/arch/loongarch/include/asm/kexec.h
>> b/arch/loongarch/include/asm/kexec.h
>> new file mode 100644
>> index 000000000000..5c9e7b5eccb8
>> --- /dev/null
>> +++ b/arch/loongarch/include/asm/kexec.h
>> @@ -0,0 +1,58 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/*
>> + * kexec.h for kexec
>> + *
>> + * Copyright (C) 2022 Loongson Technology Corporation Limited
>> + */
>> +
>> +#ifndef _ASM_KEXEC_H
>> +#define _ASM_KEXEC_H
>> +
>> +#include <asm/stacktrace.h>
>> +#include <asm/page.h>
>> +
>> +/* Maximum physical address we can use pages from */
>> +#define KEXEC_SOURCE_MEMORY_LIMIT (-1UL)
>> +/* Maximum address we can reach in physical address mode */
>> +#define KEXEC_DESTINATION_MEMORY_LIMIT (-1UL)
>> + /* Maximum address we can use for the control code buffer */
>> +#define KEXEC_CONTROL_MEMORY_LIMIT (-1UL)
>> +
>> +/* Reserve a page for the control code buffer */
>> +#define KEXEC_CONTROL_PAGE_SIZE PAGE_SIZE
>> +
>> +/* The native architecture */
>> +#define KEXEC_ARCH KEXEC_ARCH_LOONGARCH
>> +
>> +static inline void crash_setup_regs(struct pt_regs *newregs,
>> +                    struct pt_regs *oldregs)
>> +{
>> +    if (oldregs)
>> +        memcpy(newregs, oldregs, sizeof(*newregs));
>> +    else
>> +        prepare_frametrace(newregs);
>> +}
>> +
>> +#define ARCH_HAS_KIMAGE_ARCH
>> +
>> +struct kimage_arch {
>> +    unsigned long boot_flag;
>> +    unsigned long fdt_addr;
>> +};
>> +
>> +typedef void (*do_kexec_t)(unsigned long boot_flag,
>> +               unsigned long fdt_addr,
>> +               unsigned long first_ind_entry,
>> +               unsigned long jump_addr);
>> +
>> +struct kimage;
>> +extern const unsigned char relocate_new_kernel[];
>> +extern const size_t relocate_new_kernel_size;
>> +
>> +#ifdef CONFIG_SMP
>> +extern atomic_t kexec_ready_to_reboot;
>> +extern const unsigned char kexec_smp_wait[];
>> +extern void kexec_reboot(void);
>> +#endif
>> +
>> +#endif /* !_ASM_KEXEC_H */
>> diff --git a/arch/loongarch/kernel/Makefile
>> b/arch/loongarch/kernel/Makefile
>> index a213e994db68..20b64ac3f128 100644
>> --- a/arch/loongarch/kernel/Makefile
>> +++ b/arch/loongarch/kernel/Makefile
>> @@ -17,6 +17,8 @@ obj-$(CONFIG_CPU_HAS_FPU)    += fpu.o
>>   obj-$(CONFIG_MODULES)        += module.o module-sections.o
>>   obj-$(CONFIG_STACKTRACE)    += stacktrace.o
>>   +obj-$(CONFIG_KEXEC)             += machine_kexec.o relocate_kernel.o
>> +
>>   obj-$(CONFIG_PROC_FS)        += proc.o
>>     obj-$(CONFIG_SMP)        += smp.o
>> diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S
>> index 01bac62a6442..22bdf4928325 100644
>> --- a/arch/loongarch/kernel/head.S
>> +++ b/arch/loongarch/kernel/head.S
>> @@ -20,7 +20,12 @@
>>     _head:
>>       .word    MZ_MAGIC        /* "MZ", MS-DOS header */
>> -    .org    0x3c            /* 0x04 ~ 0x3b reserved */
>> +    .org    0x8
>> +    .quad    0            /* Image load offset from start of RAM */
>> +    .dword    _end - _text        /* Effective size of kernel image */
>> +    .quad    0
>> +    .dword    kernel_entry        /* Kernel entry point */
>> +    .org    0x3c            /* 0x28 ~ 0x3b reserved */
>>       .long    pe_header - _head    /* Offset to the PE header */
>>     pe_header:
>> diff --git a/arch/loongarch/kernel/machine_kexec.c
>> b/arch/loongarch/kernel/machine_kexec.c
>> new file mode 100644
>> index 000000000000..4ffcd4cd9c8c
>> --- /dev/null
>> +++ b/arch/loongarch/kernel/machine_kexec.c
>> @@ -0,0 +1,178 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * machine_kexec.c for kexec
>> + *
>> + * Copyright (C) 2022 Loongson Technology Corporation Limited
>> + */
>> +#include <linux/compiler.h>
>> +#include <linux/cpu.h>
>> +#include <linux/kexec.h>
>> +#include <linux/mm.h>
>> +#include <linux/delay.h>
>> +#include <linux/libfdt.h>
>> +#include <linux/of_fdt.h>
>> +
>> +#include <asm/bootinfo.h>
>> +#include <asm/cacheflush.h>
>> +#include <asm/page.h>
>> +
>> +/* 0x100000 ~ 0x200000 is safe */
>> +#define KEXEC_CTRL_CODE    TO_CACHE(0x100000UL)
>> +#define KEXEC_BLOB_ADDR    TO_CACHE(0x108000UL)
>> +
>> +static unsigned long reboot_code_buffer;
>> +#ifdef CONFIG_SMP
>> +void (*relocated_kexec_smp_wait)(void *);
>> +atomic_t kexec_ready_to_reboot = ATOMIC_INIT(0);
>> +#endif
>> +
>> +static unsigned long jump_addr;
>> +static unsigned long first_ind_entry;
>> +static unsigned long boot_flag;
>> +static unsigned long fdt_addr;
>> +
>> +static void kexec_image_info(const struct kimage *kimage)
>> +{
>> +    unsigned long i;
>> +
>> +    pr_debug("kexec kimage info:\n");
>> +    pr_debug("\ttype:        %d\n", kimage->type);
>> +    pr_debug("\tstart:       %lx\n", kimage->start);
>> +    pr_debug("\thead:        %lx\n", kimage->head);
>> +    pr_debug("\tnr_segments: %lu\n", kimage->nr_segments);
>> +
>> +    for (i = 0; i < kimage->nr_segments; i++) {
>> +        pr_debug("\t    segment[%lu]: %016lx - %016lx", i,
>> +            kimage->segment[i].mem,
>> +            kimage->segment[i].mem + kimage->segment[i].memsz);
>> +        pr_debug("\t\t0x%lx bytes, %lu pages\n",
>> +            (unsigned long)kimage->segment[i].memsz,
>> +            (unsigned long)kimage->segment[i].memsz /  PAGE_SIZE);
>> +    }
>> +}
>> +
>> +int machine_kexec_prepare(struct kimage *kimage)
>> +{
>> +    int i;
>> +    void *dtb = (void *)KEXEC_BLOB_ADDR;
>> +
>> +    kexec_image_info(kimage);
>> +
>> +    /* Find the Flattened Device Tree */
>> +    for (i = 0; i < kimage->nr_segments; i++) {
>> +        if (!fdt_check_header(kimage->segment[i].buf)) {
>> +            memcpy(dtb, kimage->segment[i].buf, SZ_64K);
>> +            kimage->arch.boot_flag = fw_arg0;
>> +            kimage->arch.fdt_addr = (unsigned long) dtb;
>> +            break;
>> +        }
>> +        continue;
>> +    }
>> +
>> +    /* kexec need a safe page to save reboot_code_buffer */
>> +    kimage->control_code_page = virt_to_page((void *)KEXEC_CTRL_CODE);
>> +
>> +    reboot_code_buffer =
>> +      (unsigned long)page_address(kimage->control_code_page);
>> +    memcpy((void *)reboot_code_buffer, relocate_new_kernel,
>> +           relocate_new_kernel_size);
> It copys same content to KEXEC_CTRL_CODE each time, could we do this at
> boot time?
I think it's possible to have the copy action happen at boot-time or
during the prepare phase. (RISCV in prepare, MIPS in boot-time)

>
> BTW, our system always keep the low-2MB no used, on mips-loongson or
> LoongArch. Is that necessary on LoongArch? We cannot use parameter
> 'mem=YYM' normally but 'mem=YYM@2M' is ok. And the low-2MB is not
> in virtual memory management, although we can get it in kernel.
For existing kernels, the low 2M has been reserved by
memblock_reserve(PHYS_OFFSET, 0x200000), maybe it is acceptable to keep
the low 2M behavior.

Yes, we need to use "mem=YM@2M" if the low 2M is reserved.

>
> In kexec/kdump process, we can follows kimage_alloc_control_pages().
> When the boot cpu copy complete the second-kernels, all cpus can jump
> to a kernel-entry-trampoline which is in kernel image. Then we don't
> worry about the code can be destroyed. The kernel-entry-trampoline
> get its cpuid, keep non-boot cpus do as kexec_smp_wait and let boot
> cpu go kernel-entry. In this way we can drop the low-2MB IMO.

It is also feasible to dynamically allocate control pages, but it is
easier to use a low 2M approach. What do you think, Huacai?

>
>> +
>> +    /* All secondary cpus now may jump to kexec_smp_wait cycle */
>> +    relocated_kexec_smp_wait = reboot_code_buffer +
>> +        (void *)(kexec_smp_wait - relocate_new_kernel);
>> +
>> +    return 0;
>> +}
>> +
>> +void machine_kexec_cleanup(struct kimage *kimage)
>> +{
>> +}
>> +
>> +#ifdef CONFIG_SMP
>> +void kexec_reboot(void)
>> +{
>> +    do_kexec_t do_kexec = NULL;
>> +
>> +    /* All secondary cpus go to kexec_smp_wait */
>> +    if (smp_processor_id() > 0) {
>> +        relocated_kexec_smp_wait(NULL);
>> +        unreachable();
>> +    }
>> +
>> +    do_kexec = (void *)reboot_code_buffer;
>> +    do_kexec(boot_flag, fdt_addr, first_ind_entry, jump_addr);
>> +
>> +    unreachable();
>> +}
>> +
>> +static void kexec_shutdown_secondary(void *)
>> +{
>> +    local_irq_disable();
>> +    while (!atomic_read(&kexec_ready_to_reboot))
>> +        cpu_relax();
>> +
>> +    kexec_reboot();
>> +}
>> +
>> +void machine_crash_shutdown(struct pt_regs *regs)
>> +{
>> +}
>> +#endif
>> +
>> +void machine_shutdown(void)
>> +{
>> +    smp_call_function(kexec_shutdown_secondary, NULL, 0);
>> +}
>> +
>> +void machine_kexec(struct kimage *image)
>> +{
>> +    unsigned long entry;
>> +    unsigned long *ptr;
>> +    struct kimage_arch *internal = &image->arch;
>> +
>> +    boot_flag = internal->boot_flag;
>> +    fdt_addr = internal->fdt_addr;
>> +
>> +    jump_addr = (unsigned long)phys_to_virt(image->start);
>> +
>> +    first_ind_entry = (unsigned long)phys_to_virt(image->head &
>> PAGE_MASK);
>> +
>> +    /*
>> +     * The generic kexec code builds a page list with physical
>> +     * addresses. they are directly accessible through XKPRANGE
>> +     * hence the phys_to_virt() call.
>> +     */
>> +    for (ptr = &image->head; (entry = *ptr) && !(entry & IND_DONE);
>> +         ptr = (entry & IND_INDIRECTION) ?
>> +           phys_to_virt(entry & PAGE_MASK) : ptr + 1) {
>> +        if (*ptr & IND_SOURCE || *ptr & IND_INDIRECTION ||
>> +            *ptr & IND_DESTINATION)
>> +            *ptr = (unsigned long) phys_to_virt(*ptr);
>> +    }
>> +
>> +    /* Mark offline before disabling local irq. */
>> +    set_cpu_online(smp_processor_id(), false);
>> +
>> +    /* we do not want to be bothered. */
>> +    local_irq_disable();
>> +
>> +    pr_notice("Will call new kernel at %lx\n", jump_addr);
>> +    pr_notice("FDT image at %lx\n", fdt_addr);
>> +    pr_notice("Bye ...\n");
>> +
>> +    /* Make reboot code buffer available to the boot CPU. */
>> +    flush_cache_all();
>> +
>> +    atomic_set(&kexec_ready_to_reboot, 1);
>> +
>> +    /*
>> +     * We know we were online, and there will be no incoming IPIs at
>> +     * this point.
>> +     */
>> +    set_cpu_online(smp_processor_id(), true);
>> +
>> +    /* Ensure remote CPUs observe that we're online before rebooting. */
>> +    smp_mb__after_atomic();
>> +
>> +    kexec_reboot();
>> +}
>> diff --git a/arch/loongarch/kernel/relocate_kernel.S
>> b/arch/loongarch/kernel/relocate_kernel.S
>> new file mode 100644
>> index 000000000000..d1f242f74ea8
>> --- /dev/null
>> +++ b/arch/loongarch/kernel/relocate_kernel.S
>> @@ -0,0 +1,125 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/*
>> + * relocate_kernel.S for kexec
>> + *
>> + * Copyright (C) 2022 Loongson Technology Corporation Limited
>> + */
>> +
>> +#include <linux/kexec.h>
>> +
>> +#include <asm/asm.h>
>> +#include <asm/asmmacro.h>
>> +#include <asm/regdef.h>
>> +#include <asm/loongarch.h>
>> +#include <asm/stackframe.h>
>> +#include <asm/addrspace.h>
>> +
>> +#define IPI_REG_BASE 0x1fe01000
>> +
>> +SYM_CODE_START(relocate_new_kernel)
>> +    /*
>> +     * s0: Boot flag passed to the new kernel
>> +     * s1: Virt address of the FDT image
>> +     * s2: Pointer to the current entry
>> +     * s3: Virt address to jump to after relocation
>> +     */
>> +    move        s0, a0
>> +    move        s1, a1
>> +    move        s2, a2
>> +    move        s3, a3
>> +
>> +process_entry:
>> +    PTR_L        s4, s2, 0
>> +    PTR_ADDI    s2, s2, SZREG
>> +
>> +    /* destination page */
>> +    andi        s5, s4, IND_DESTINATION
>> +    beqz        s5, 1f
>> +    li.w        t0, ~0x1
>> +    and        s6, s4, t0    /* store destination addr in s6 */
>> +    b        process_entry
>> +
>> +1:
>> +    /* indirection page, update s2    */
>> +    andi        s5, s4, IND_INDIRECTION
>> +    beqz        s5, 1f
>> +    li.w        t0, ~0x2
>> +    and        s2, s4, t0
>> +    b        process_entry
>> +
>> +1:
>> +    /* done page */
>> +    andi        s5, s4, IND_DONE
>> +    beqz        s5, 1f
>> +    b        done
>> +1:
>> +    /* source page */
>> +    andi        s5, s4, IND_SOURCE
>> +    beqz        s5, process_entry
>> +    li.w        t0, ~0x8
>> +    and        s4, s4, t0
>> +    li.w        s8, (1 << _PAGE_SHIFT) / SZREG
>> +
>> +copy_word:
>> +    /* copy page word by word */
>> +    REG_L        s7, s4, 0
>> +    REG_S        s7, s6, 0
>> +    PTR_ADDI    s6, s6, SZREG
>> +    PTR_ADDI    s4, s4, SZREG
>> +    LONG_ADDI    s8, s8, -1
>> +    beqz        s8, process_entry
>> +    b        copy_word
>> +    b        process_entry
>> +
>> +done:
>> +    dbar        0
> ibar, too?

Will add ibar 0.

>> +
>> +    move        a0, s0
>> +    move        a1, s1
>> +    /* jump to the new kernel */
>> +    jr        s3
>> +SYM_CODE_END(relocate_new_kernel)
>> +
>> +#ifdef CONFIG_SMP
>> +/*
>> + * Other CPUs should wait until code is relocated and
>> + * then start at entry (?) point.
>> + */
>> +SYM_CODE_START(kexec_smp_wait)
>> +    li.d        t0, IPI_REG_BASE
>> +    li.d        t1, UNCACHE_BASE
>> +    or        t0, t0, t1
>> +
>> +    /*
>> +     * s1:initfn
>> +     * t0:base t1:cpuid t2:node t3:core t4:count
>> +     */
>> +    csrrd        t1, LOONGARCH_CSR_CPUID
>> +    andi        t1, t1, CSR_CPUID_COREID
>> +    andi        t3, t1, 0x3
>> +    slli.w        t3, t3, 8              /* get core id */
>> +    or        t0, t0, t3
>> +    andi        t2, t1, 0x3c
>> +    slli.d        t2, t2, 42             /* get node id */
>> +    or        t0, t0, t2
>> +
>> +1:    li.w        t4, 0x100              /* wait for init loop */
>> +2:    addi.w        t4, t4, -1             /* limit mailbox access */
>> +    bnez        t4, 2b
>> +    ld.w        s1, t0, 0x20           /* check PC as an indicator */
> Can we do this with iocsr*?

OK, I will consider the implementation in the iocsr way.

Thanks,
Youling
>
> Thanks,
> Jinyang
>> +    beqz        s1, 1b
>> +    ld.d        s1, t0, 0x20           /* get PC via mailbox */
>> +    ld.d        sp, t0, 0x28           /* get SP via mailbox */
>> +    ld.d        tp, t0, 0x30           /* get TP via mailbox */
>> +
>> +    li.d        t0, CACHE_BASE
>> +    or        s1, s1, t0
>> +    jr        s1                     /* jump to initial PC */
>> +SYM_CODE_END(kexec_smp_wait)
>> +#endif
>> +
>> +relocate_new_kernel_end:
>> +
>> +SYM_DATA_START(relocate_new_kernel_size)
>> +    PTR        relocate_new_kernel_end - relocate_new_kernel
>> +SYM_DATA_END(relocate_new_kernel_size)
>

Re: [PATCH 1/3] LoongArch: Add kexec support

Posted by Huacai Chen 3 years, 7 months ago

On Tue, Aug 30, 2022 at 11:26 AM Youling Tang <tangyouling@loongson.cn> wrote:
>
> Hi, Jinyang
>
> On 08/30/2022 09:53 AM, Jinyang He wrote:
> > Hi, Youling,
> >
> >
> > On 08/29/2022 12:37 PM, Youling Tang wrote:
> >> Add three new files, kexec.h, machine_kexec.c and relocate_kernel.S to
> >> the
> >> LoongArch architecture that add support for the kexec re-boot mechanis
> >> (CONFIG_KEXEC) on LoongArch platforms.
> >>
> >> Supports loading vmlinux (vmlinux.elf) in ELF format and vmlinux.efi in
> >> PE format.
> >>
> >> I tested this on  LoongArch 3A5000 machine and works as expected,
> >>
> >>   $ sudo kexec -l /boot/vmlinux.efi --reuse-cmdline
> >>   $ sudo kexec -e
> >>
> >> Signed-off-by: Youling Tang <tangyouling@loongson.cn>
> >> ---
> >>   arch/loongarch/Kconfig                  |  11 ++
> >>   arch/loongarch/include/asm/kexec.h      |  58 ++++++++
> >>   arch/loongarch/kernel/Makefile          |   2 +
> >>   arch/loongarch/kernel/head.S            |   7 +-
> >>   arch/loongarch/kernel/machine_kexec.c   | 178 ++++++++++++++++++++++++
> >>   arch/loongarch/kernel/relocate_kernel.S | 125 +++++++++++++++++
> >>   6 files changed, 380 insertions(+), 1 deletion(-)
> >>   create mode 100644 arch/loongarch/include/asm/kexec.h
> >>   create mode 100644 arch/loongarch/kernel/machine_kexec.c
> >>   create mode 100644 arch/loongarch/kernel/relocate_kernel.S
> >>
> >> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> >> index 45364cffc793..903c82fa958d 100644
> >> --- a/arch/loongarch/Kconfig
> >> +++ b/arch/loongarch/Kconfig
> >> @@ -409,6 +409,17 @@ config FORCE_MAX_ZONEORDER
> >>         The page size is not necessarily 4KB.  Keep this in mind
> >>         when choosing a value for this option.
> >>   +config KEXEC
> >> +    bool "Kexec system call"
> >> +    select KEXEC_CORE
> >> +    help
> >> +      kexec is a system call that implements the ability to shutdown
> >> your
> >> +      current kernel, and to start another kernel.  It is like a reboot
> >> +      but it is independent of the system firmware.   And like a reboot
> >> +      you can start any kernel with it, not just Linux.
> >> +
> >> +      The name comes from the similarity to the exec system call.
> >> +
> >>   config SECCOMP
> >>       bool "Enable seccomp to safely compute untrusted bytecode"
> >>       depends on PROC_FS
> >> diff --git a/arch/loongarch/include/asm/kexec.h
> >> b/arch/loongarch/include/asm/kexec.h
> >> new file mode 100644
> >> index 000000000000..5c9e7b5eccb8
> >> --- /dev/null
> >> +++ b/arch/loongarch/include/asm/kexec.h
> >> @@ -0,0 +1,58 @@
> >> +/* SPDX-License-Identifier: GPL-2.0 */
> >> +/*
> >> + * kexec.h for kexec
> >> + *
> >> + * Copyright (C) 2022 Loongson Technology Corporation Limited
> >> + */
> >> +
> >> +#ifndef _ASM_KEXEC_H
> >> +#define _ASM_KEXEC_H
> >> +
> >> +#include <asm/stacktrace.h>
> >> +#include <asm/page.h>
> >> +
> >> +/* Maximum physical address we can use pages from */
> >> +#define KEXEC_SOURCE_MEMORY_LIMIT (-1UL)
> >> +/* Maximum address we can reach in physical address mode */
> >> +#define KEXEC_DESTINATION_MEMORY_LIMIT (-1UL)
> >> + /* Maximum address we can use for the control code buffer */
> >> +#define KEXEC_CONTROL_MEMORY_LIMIT (-1UL)
> >> +
> >> +/* Reserve a page for the control code buffer */
> >> +#define KEXEC_CONTROL_PAGE_SIZE PAGE_SIZE
> >> +
> >> +/* The native architecture */
> >> +#define KEXEC_ARCH KEXEC_ARCH_LOONGARCH
> >> +
> >> +static inline void crash_setup_regs(struct pt_regs *newregs,
> >> +                    struct pt_regs *oldregs)
> >> +{
> >> +    if (oldregs)
> >> +        memcpy(newregs, oldregs, sizeof(*newregs));
> >> +    else
> >> +        prepare_frametrace(newregs);
> >> +}
> >> +
> >> +#define ARCH_HAS_KIMAGE_ARCH
> >> +
> >> +struct kimage_arch {
> >> +    unsigned long boot_flag;
> >> +    unsigned long fdt_addr;
> >> +};
> >> +
> >> +typedef void (*do_kexec_t)(unsigned long boot_flag,
> >> +               unsigned long fdt_addr,
> >> +               unsigned long first_ind_entry,
> >> +               unsigned long jump_addr);
> >> +
> >> +struct kimage;
> >> +extern const unsigned char relocate_new_kernel[];
> >> +extern const size_t relocate_new_kernel_size;
> >> +
> >> +#ifdef CONFIG_SMP
> >> +extern atomic_t kexec_ready_to_reboot;
> >> +extern const unsigned char kexec_smp_wait[];
> >> +extern void kexec_reboot(void);
> >> +#endif
> >> +
> >> +#endif /* !_ASM_KEXEC_H */
> >> diff --git a/arch/loongarch/kernel/Makefile
> >> b/arch/loongarch/kernel/Makefile
> >> index a213e994db68..20b64ac3f128 100644
> >> --- a/arch/loongarch/kernel/Makefile
> >> +++ b/arch/loongarch/kernel/Makefile
> >> @@ -17,6 +17,8 @@ obj-$(CONFIG_CPU_HAS_FPU)    += fpu.o
> >>   obj-$(CONFIG_MODULES)        += module.o module-sections.o
> >>   obj-$(CONFIG_STACKTRACE)    += stacktrace.o
> >>   +obj-$(CONFIG_KEXEC)             += machine_kexec.o relocate_kernel.o
> >> +
> >>   obj-$(CONFIG_PROC_FS)        += proc.o
> >>     obj-$(CONFIG_SMP)        += smp.o
> >> diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S
> >> index 01bac62a6442..22bdf4928325 100644
> >> --- a/arch/loongarch/kernel/head.S
> >> +++ b/arch/loongarch/kernel/head.S
> >> @@ -20,7 +20,12 @@
> >>     _head:
> >>       .word    MZ_MAGIC        /* "MZ", MS-DOS header */
> >> -    .org    0x3c            /* 0x04 ~ 0x3b reserved */
> >> +    .org    0x8
> >> +    .quad    0            /* Image load offset from start of RAM */
> >> +    .dword    _end - _text        /* Effective size of kernel image */
> >> +    .quad    0
> >> +    .dword    kernel_entry        /* Kernel entry point */
> >> +    .org    0x3c            /* 0x28 ~ 0x3b reserved */
> >>       .long    pe_header - _head    /* Offset to the PE header */
> >>     pe_header:
> >> diff --git a/arch/loongarch/kernel/machine_kexec.c
> >> b/arch/loongarch/kernel/machine_kexec.c
> >> new file mode 100644
> >> index 000000000000..4ffcd4cd9c8c
> >> --- /dev/null
> >> +++ b/arch/loongarch/kernel/machine_kexec.c
> >> @@ -0,0 +1,178 @@
> >> +// SPDX-License-Identifier: GPL-2.0-only
> >> +/*
> >> + * machine_kexec.c for kexec
> >> + *
> >> + * Copyright (C) 2022 Loongson Technology Corporation Limited
> >> + */
> >> +#include <linux/compiler.h>
> >> +#include <linux/cpu.h>
> >> +#include <linux/kexec.h>
> >> +#include <linux/mm.h>
> >> +#include <linux/delay.h>
> >> +#include <linux/libfdt.h>
> >> +#include <linux/of_fdt.h>
> >> +
> >> +#include <asm/bootinfo.h>
> >> +#include <asm/cacheflush.h>
> >> +#include <asm/page.h>
> >> +
> >> +/* 0x100000 ~ 0x200000 is safe */
> >> +#define KEXEC_CTRL_CODE    TO_CACHE(0x100000UL)
> >> +#define KEXEC_BLOB_ADDR    TO_CACHE(0x108000UL)
> >> +
> >> +static unsigned long reboot_code_buffer;
> >> +#ifdef CONFIG_SMP
> >> +void (*relocated_kexec_smp_wait)(void *);
> >> +atomic_t kexec_ready_to_reboot = ATOMIC_INIT(0);
> >> +#endif
> >> +
> >> +static unsigned long jump_addr;
> >> +static unsigned long first_ind_entry;
> >> +static unsigned long boot_flag;
> >> +static unsigned long fdt_addr;
> >> +
> >> +static void kexec_image_info(const struct kimage *kimage)
> >> +{
> >> +    unsigned long i;
> >> +
> >> +    pr_debug("kexec kimage info:\n");
> >> +    pr_debug("\ttype:        %d\n", kimage->type);
> >> +    pr_debug("\tstart:       %lx\n", kimage->start);
> >> +    pr_debug("\thead:        %lx\n", kimage->head);
> >> +    pr_debug("\tnr_segments: %lu\n", kimage->nr_segments);
> >> +
> >> +    for (i = 0; i < kimage->nr_segments; i++) {
> >> +        pr_debug("\t    segment[%lu]: %016lx - %016lx", i,
> >> +            kimage->segment[i].mem,
> >> +            kimage->segment[i].mem + kimage->segment[i].memsz);
> >> +        pr_debug("\t\t0x%lx bytes, %lu pages\n",
> >> +            (unsigned long)kimage->segment[i].memsz,
> >> +            (unsigned long)kimage->segment[i].memsz /  PAGE_SIZE);
> >> +    }
> >> +}
> >> +
> >> +int machine_kexec_prepare(struct kimage *kimage)
> >> +{
> >> +    int i;
> >> +    void *dtb = (void *)KEXEC_BLOB_ADDR;
> >> +
> >> +    kexec_image_info(kimage);
> >> +
> >> +    /* Find the Flattened Device Tree */
> >> +    for (i = 0; i < kimage->nr_segments; i++) {
> >> +        if (!fdt_check_header(kimage->segment[i].buf)) {
> >> +            memcpy(dtb, kimage->segment[i].buf, SZ_64K);
> >> +            kimage->arch.boot_flag = fw_arg0;
> >> +            kimage->arch.fdt_addr = (unsigned long) dtb;
> >> +            break;
> >> +        }
> >> +        continue;
> >> +    }
> >> +
> >> +    /* kexec need a safe page to save reboot_code_buffer */
> >> +    kimage->control_code_page = virt_to_page((void *)KEXEC_CTRL_CODE);
> >> +
> >> +    reboot_code_buffer =
> >> +      (unsigned long)page_address(kimage->control_code_page);
> >> +    memcpy((void *)reboot_code_buffer, relocate_new_kernel,
> >> +           relocate_new_kernel_size);
> > It copys same content to KEXEC_CTRL_CODE each time, could we do this at
> > boot time?
> I think it's possible to have the copy action happen at boot-time or
> during the prepare phase. (RISCV in prepare, MIPS in boot-time)
>
> >
> > BTW, our system always keep the low-2MB no used, on mips-loongson or
> > LoongArch. Is that necessary on LoongArch? We cannot use parameter
> > 'mem=YYM' normally but 'mem=YYM@2M' is ok. And the low-2MB is not
> > in virtual memory management, although we can get it in kernel.
> For existing kernels, the low 2M has been reserved by
> memblock_reserve(PHYS_OFFSET, 0x200000), maybe it is acceptable to keep
> the low 2M behavior.
>
> Yes, we need to use "mem=YM@2M" if the low 2M is reserved.
>
> >
> > In kexec/kdump process, we can follows kimage_alloc_control_pages().
> > When the boot cpu copy complete the second-kernels, all cpus can jump
> > to a kernel-entry-trampoline which is in kernel image. Then we don't
> > worry about the code can be destroyed. The kernel-entry-trampoline
> > get its cpuid, keep non-boot cpus do as kexec_smp_wait and let boot
> > cpu go kernel-entry. In this way we can drop the low-2MB IMO.
>
> It is also feasible to dynamically allocate control pages, but it is
> easier to use a low 2M approach. What do you think, Huacai?
I prefer to use the low 2MB.

Huacai
>
> >
> >> +
> >> +    /* All secondary cpus now may jump to kexec_smp_wait cycle */
> >> +    relocated_kexec_smp_wait = reboot_code_buffer +
> >> +        (void *)(kexec_smp_wait - relocate_new_kernel);
> >> +
> >> +    return 0;
> >> +}
> >> +
> >> +void machine_kexec_cleanup(struct kimage *kimage)
> >> +{
> >> +}
> >> +
> >> +#ifdef CONFIG_SMP
> >> +void kexec_reboot(void)
> >> +{
> >> +    do_kexec_t do_kexec = NULL;
> >> +
> >> +    /* All secondary cpus go to kexec_smp_wait */
> >> +    if (smp_processor_id() > 0) {
> >> +        relocated_kexec_smp_wait(NULL);
> >> +        unreachable();
> >> +    }
> >> +
> >> +    do_kexec = (void *)reboot_code_buffer;
> >> +    do_kexec(boot_flag, fdt_addr, first_ind_entry, jump_addr);
> >> +
> >> +    unreachable();
> >> +}
> >> +
> >> +static void kexec_shutdown_secondary(void *)
> >> +{
> >> +    local_irq_disable();
> >> +    while (!atomic_read(&kexec_ready_to_reboot))
> >> +        cpu_relax();
> >> +
> >> +    kexec_reboot();
> >> +}
> >> +
> >> +void machine_crash_shutdown(struct pt_regs *regs)
> >> +{
> >> +}
> >> +#endif
> >> +
> >> +void machine_shutdown(void)
> >> +{
> >> +    smp_call_function(kexec_shutdown_secondary, NULL, 0);
> >> +}
> >> +
> >> +void machine_kexec(struct kimage *image)
> >> +{
> >> +    unsigned long entry;
> >> +    unsigned long *ptr;
> >> +    struct kimage_arch *internal = &image->arch;
> >> +
> >> +    boot_flag = internal->boot_flag;
> >> +    fdt_addr = internal->fdt_addr;
> >> +
> >> +    jump_addr = (unsigned long)phys_to_virt(image->start);
> >> +
> >> +    first_ind_entry = (unsigned long)phys_to_virt(image->head &
> >> PAGE_MASK);
> >> +
> >> +    /*
> >> +     * The generic kexec code builds a page list with physical
> >> +     * addresses. they are directly accessible through XKPRANGE
> >> +     * hence the phys_to_virt() call.
> >> +     */
> >> +    for (ptr = &image->head; (entry = *ptr) && !(entry & IND_DONE);
> >> +         ptr = (entry & IND_INDIRECTION) ?
> >> +           phys_to_virt(entry & PAGE_MASK) : ptr + 1) {
> >> +        if (*ptr & IND_SOURCE || *ptr & IND_INDIRECTION ||
> >> +            *ptr & IND_DESTINATION)
> >> +            *ptr = (unsigned long) phys_to_virt(*ptr);
> >> +    }
> >> +
> >> +    /* Mark offline before disabling local irq. */
> >> +    set_cpu_online(smp_processor_id(), false);
> >> +
> >> +    /* we do not want to be bothered. */
> >> +    local_irq_disable();
> >> +
> >> +    pr_notice("Will call new kernel at %lx\n", jump_addr);
> >> +    pr_notice("FDT image at %lx\n", fdt_addr);
> >> +    pr_notice("Bye ...\n");
> >> +
> >> +    /* Make reboot code buffer available to the boot CPU. */
> >> +    flush_cache_all();
> >> +
> >> +    atomic_set(&kexec_ready_to_reboot, 1);
> >> +
> >> +    /*
> >> +     * We know we were online, and there will be no incoming IPIs at
> >> +     * this point.
> >> +     */
> >> +    set_cpu_online(smp_processor_id(), true);
> >> +
> >> +    /* Ensure remote CPUs observe that we're online before rebooting. */
> >> +    smp_mb__after_atomic();
> >> +
> >> +    kexec_reboot();
> >> +}
> >> diff --git a/arch/loongarch/kernel/relocate_kernel.S
> >> b/arch/loongarch/kernel/relocate_kernel.S
> >> new file mode 100644
> >> index 000000000000..d1f242f74ea8
> >> --- /dev/null
> >> +++ b/arch/loongarch/kernel/relocate_kernel.S
> >> @@ -0,0 +1,125 @@
> >> +/* SPDX-License-Identifier: GPL-2.0 */
> >> +/*
> >> + * relocate_kernel.S for kexec
> >> + *
> >> + * Copyright (C) 2022 Loongson Technology Corporation Limited
> >> + */
> >> +
> >> +#include <linux/kexec.h>
> >> +
> >> +#include <asm/asm.h>
> >> +#include <asm/asmmacro.h>
> >> +#include <asm/regdef.h>
> >> +#include <asm/loongarch.h>
> >> +#include <asm/stackframe.h>
> >> +#include <asm/addrspace.h>
> >> +
> >> +#define IPI_REG_BASE 0x1fe01000
> >> +
> >> +SYM_CODE_START(relocate_new_kernel)
> >> +    /*
> >> +     * s0: Boot flag passed to the new kernel
> >> +     * s1: Virt address of the FDT image
> >> +     * s2: Pointer to the current entry
> >> +     * s3: Virt address to jump to after relocation
> >> +     */
> >> +    move        s0, a0
> >> +    move        s1, a1
> >> +    move        s2, a2
> >> +    move        s3, a3
> >> +
> >> +process_entry:
> >> +    PTR_L        s4, s2, 0
> >> +    PTR_ADDI    s2, s2, SZREG
> >> +
> >> +    /* destination page */
> >> +    andi        s5, s4, IND_DESTINATION
> >> +    beqz        s5, 1f
> >> +    li.w        t0, ~0x1
> >> +    and        s6, s4, t0    /* store destination addr in s6 */
> >> +    b        process_entry
> >> +
> >> +1:
> >> +    /* indirection page, update s2    */
> >> +    andi        s5, s4, IND_INDIRECTION
> >> +    beqz        s5, 1f
> >> +    li.w        t0, ~0x2
> >> +    and        s2, s4, t0
> >> +    b        process_entry
> >> +
> >> +1:
> >> +    /* done page */
> >> +    andi        s5, s4, IND_DONE
> >> +    beqz        s5, 1f
> >> +    b        done
> >> +1:
> >> +    /* source page */
> >> +    andi        s5, s4, IND_SOURCE
> >> +    beqz        s5, process_entry
> >> +    li.w        t0, ~0x8
> >> +    and        s4, s4, t0
> >> +    li.w        s8, (1 << _PAGE_SHIFT) / SZREG
> >> +
> >> +copy_word:
> >> +    /* copy page word by word */
> >> +    REG_L        s7, s4, 0
> >> +    REG_S        s7, s6, 0
> >> +    PTR_ADDI    s6, s6, SZREG
> >> +    PTR_ADDI    s4, s4, SZREG
> >> +    LONG_ADDI    s8, s8, -1
> >> +    beqz        s8, process_entry
> >> +    b        copy_word
> >> +    b        process_entry
> >> +
> >> +done:
> >> +    dbar        0
> > ibar, too?
>
> Will add ibar 0.
>
> >> +
> >> +    move        a0, s0
> >> +    move        a1, s1
> >> +    /* jump to the new kernel */
> >> +    jr        s3
> >> +SYM_CODE_END(relocate_new_kernel)
> >> +
> >> +#ifdef CONFIG_SMP
> >> +/*
> >> + * Other CPUs should wait until code is relocated and
> >> + * then start at entry (?) point.
> >> + */
> >> +SYM_CODE_START(kexec_smp_wait)
> >> +    li.d        t0, IPI_REG_BASE
> >> +    li.d        t1, UNCACHE_BASE
> >> +    or        t0, t0, t1
> >> +
> >> +    /*
> >> +     * s1:initfn
> >> +     * t0:base t1:cpuid t2:node t3:core t4:count
> >> +     */
> >> +    csrrd        t1, LOONGARCH_CSR_CPUID
> >> +    andi        t1, t1, CSR_CPUID_COREID
> >> +    andi        t3, t1, 0x3
> >> +    slli.w        t3, t3, 8              /* get core id */
> >> +    or        t0, t0, t3
> >> +    andi        t2, t1, 0x3c
> >> +    slli.d        t2, t2, 42             /* get node id */
> >> +    or        t0, t0, t2
> >> +
> >> +1:    li.w        t4, 0x100              /* wait for init loop */
> >> +2:    addi.w        t4, t4, -1             /* limit mailbox access */
> >> +    bnez        t4, 2b
> >> +    ld.w        s1, t0, 0x20           /* check PC as an indicator */
> > Can we do this with iocsr*?
>
> OK, I will consider the implementation in the iocsr way.
>
> Thanks,
> Youling
> >
> > Thanks,
> > Jinyang
> >> +    beqz        s1, 1b
> >> +    ld.d        s1, t0, 0x20           /* get PC via mailbox */
> >> +    ld.d        sp, t0, 0x28           /* get SP via mailbox */
> >> +    ld.d        tp, t0, 0x30           /* get TP via mailbox */
> >> +
> >> +    li.d        t0, CACHE_BASE
> >> +    or        s1, s1, t0
> >> +    jr        s1                     /* jump to initial PC */
> >> +SYM_CODE_END(kexec_smp_wait)
> >> +#endif
> >> +
> >> +relocate_new_kernel_end:
> >> +
> >> +SYM_DATA_START(relocate_new_kernel_size)
> >> +    PTR        relocate_new_kernel_end - relocate_new_kernel
> >> +SYM_DATA_END(relocate_new_kernel_size)
> >
>

Re: [PATCH 1/3] LoongArch: Add kexec support

Posted by Jinyang He 3 years, 7 months ago

On 08/30/2022 11:42 AM, Huacai Chen wrote:

> On Tue, Aug 30, 2022 at 11:26 AM Youling Tang <tangyouling@loongson.cn> wrote:
>> Hi, Jinyang
>>
>> On 08/30/2022 09:53 AM, Jinyang He wrote:
>>> Hi, Youling,
>>>
>>>
>>> On 08/29/2022 12:37 PM, Youling Tang wrote:
>>>> Add three new files, kexec.h, machine_kexec.c and relocate_kernel.S to
>>>> the
>>>> LoongArch architecture that add support for the kexec re-boot mechanis
>>>> (CONFIG_KEXEC) on LoongArch platforms.
>>>>
>>>> Supports loading vmlinux (vmlinux.elf) in ELF format and vmlinux.efi in
>>>> PE format.
>>>>
>>>> I tested this on  LoongArch 3A5000 machine and works as expected,
>>>>
>>>>    $ sudo kexec -l /boot/vmlinux.efi --reuse-cmdline
>>>>    $ sudo kexec -e
>>>>
>>>> Signed-off-by: Youling Tang <tangyouling@loongson.cn>
>>>> ---
>>>>    arch/loongarch/Kconfig                  |  11 ++
>>>>    arch/loongarch/include/asm/kexec.h      |  58 ++++++++
>>>>    arch/loongarch/kernel/Makefile          |   2 +
>>>>    arch/loongarch/kernel/head.S            |   7 +-
>>>>    arch/loongarch/kernel/machine_kexec.c   | 178 ++++++++++++++++++++++++
>>>>    arch/loongarch/kernel/relocate_kernel.S | 125 +++++++++++++++++
>>>>    6 files changed, 380 insertions(+), 1 deletion(-)
>>>>    create mode 100644 arch/loongarch/include/asm/kexec.h
>>>>    create mode 100644 arch/loongarch/kernel/machine_kexec.c
>>>>    create mode 100644 arch/loongarch/kernel/relocate_kernel.S
>>>>
>>>> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
>>>> index 45364cffc793..903c82fa958d 100644
>>>> --- a/arch/loongarch/Kconfig
>>>> +++ b/arch/loongarch/Kconfig
>>>> @@ -409,6 +409,17 @@ config FORCE_MAX_ZONEORDER
>>>>          The page size is not necessarily 4KB.  Keep this in mind
>>>>          when choosing a value for this option.
>>>>    +config KEXEC
>>>> +    bool "Kexec system call"
>>>> +    select KEXEC_CORE
>>>> +    help
>>>> +      kexec is a system call that implements the ability to shutdown
>>>> your
>>>> +      current kernel, and to start another kernel.  It is like a reboot
>>>> +      but it is independent of the system firmware.   And like a reboot
>>>> +      you can start any kernel with it, not just Linux.
>>>> +
>>>> +      The name comes from the similarity to the exec system call.
>>>> +
>>>>    config SECCOMP
>>>>        bool "Enable seccomp to safely compute untrusted bytecode"
>>>>        depends on PROC_FS
>>>> diff --git a/arch/loongarch/include/asm/kexec.h
>>>> b/arch/loongarch/include/asm/kexec.h
>>>> new file mode 100644
>>>> index 000000000000..5c9e7b5eccb8
>>>> --- /dev/null
>>>> +++ b/arch/loongarch/include/asm/kexec.h
>>>> @@ -0,0 +1,58 @@
>>>> +/* SPDX-License-Identifier: GPL-2.0 */
>>>> +/*
>>>> + * kexec.h for kexec
>>>> + *
>>>> + * Copyright (C) 2022 Loongson Technology Corporation Limited
>>>> + */
>>>> +
>>>> +#ifndef _ASM_KEXEC_H
>>>> +#define _ASM_KEXEC_H
>>>> +
>>>> +#include <asm/stacktrace.h>
>>>> +#include <asm/page.h>
>>>> +
>>>> +/* Maximum physical address we can use pages from */
>>>> +#define KEXEC_SOURCE_MEMORY_LIMIT (-1UL)
>>>> +/* Maximum address we can reach in physical address mode */
>>>> +#define KEXEC_DESTINATION_MEMORY_LIMIT (-1UL)
>>>> + /* Maximum address we can use for the control code buffer */
>>>> +#define KEXEC_CONTROL_MEMORY_LIMIT (-1UL)
>>>> +
>>>> +/* Reserve a page for the control code buffer */
>>>> +#define KEXEC_CONTROL_PAGE_SIZE PAGE_SIZE
>>>> +
>>>> +/* The native architecture */
>>>> +#define KEXEC_ARCH KEXEC_ARCH_LOONGARCH
>>>> +
>>>> +static inline void crash_setup_regs(struct pt_regs *newregs,
>>>> +                    struct pt_regs *oldregs)
>>>> +{
>>>> +    if (oldregs)
>>>> +        memcpy(newregs, oldregs, sizeof(*newregs));
>>>> +    else
>>>> +        prepare_frametrace(newregs);
>>>> +}
>>>> +
>>>> +#define ARCH_HAS_KIMAGE_ARCH
>>>> +
>>>> +struct kimage_arch {
>>>> +    unsigned long boot_flag;
>>>> +    unsigned long fdt_addr;
>>>> +};
>>>> +
>>>> +typedef void (*do_kexec_t)(unsigned long boot_flag,
>>>> +               unsigned long fdt_addr,
>>>> +               unsigned long first_ind_entry,
>>>> +               unsigned long jump_addr);
>>>> +
>>>> +struct kimage;
>>>> +extern const unsigned char relocate_new_kernel[];
>>>> +extern const size_t relocate_new_kernel_size;
>>>> +
>>>> +#ifdef CONFIG_SMP
>>>> +extern atomic_t kexec_ready_to_reboot;
>>>> +extern const unsigned char kexec_smp_wait[];
>>>> +extern void kexec_reboot(void);
>>>> +#endif
>>>> +
>>>> +#endif /* !_ASM_KEXEC_H */
>>>> diff --git a/arch/loongarch/kernel/Makefile
>>>> b/arch/loongarch/kernel/Makefile
>>>> index a213e994db68..20b64ac3f128 100644
>>>> --- a/arch/loongarch/kernel/Makefile
>>>> +++ b/arch/loongarch/kernel/Makefile
>>>> @@ -17,6 +17,8 @@ obj-$(CONFIG_CPU_HAS_FPU)    += fpu.o
>>>>    obj-$(CONFIG_MODULES)        += module.o module-sections.o
>>>>    obj-$(CONFIG_STACKTRACE)    += stacktrace.o
>>>>    +obj-$(CONFIG_KEXEC)             += machine_kexec.o relocate_kernel.o
>>>> +
>>>>    obj-$(CONFIG_PROC_FS)        += proc.o
>>>>      obj-$(CONFIG_SMP)        += smp.o
>>>> diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S
>>>> index 01bac62a6442..22bdf4928325 100644
>>>> --- a/arch/loongarch/kernel/head.S
>>>> +++ b/arch/loongarch/kernel/head.S
>>>> @@ -20,7 +20,12 @@
>>>>      _head:
>>>>        .word    MZ_MAGIC        /* "MZ", MS-DOS header */
>>>> -    .org    0x3c            /* 0x04 ~ 0x3b reserved */
>>>> +    .org    0x8
>>>> +    .quad    0            /* Image load offset from start of RAM */
>>>> +    .dword    _end - _text        /* Effective size of kernel image */
>>>> +    .quad    0
>>>> +    .dword    kernel_entry        /* Kernel entry point */
>>>> +    .org    0x3c            /* 0x28 ~ 0x3b reserved */
>>>>        .long    pe_header - _head    /* Offset to the PE header */
>>>>      pe_header:
>>>> diff --git a/arch/loongarch/kernel/machine_kexec.c
>>>> b/arch/loongarch/kernel/machine_kexec.c
>>>> new file mode 100644
>>>> index 000000000000..4ffcd4cd9c8c
>>>> --- /dev/null
>>>> +++ b/arch/loongarch/kernel/machine_kexec.c
>>>> @@ -0,0 +1,178 @@
>>>> +// SPDX-License-Identifier: GPL-2.0-only
>>>> +/*
>>>> + * machine_kexec.c for kexec
>>>> + *
>>>> + * Copyright (C) 2022 Loongson Technology Corporation Limited
>>>> + */
>>>> +#include <linux/compiler.h>
>>>> +#include <linux/cpu.h>
>>>> +#include <linux/kexec.h>
>>>> +#include <linux/mm.h>
>>>> +#include <linux/delay.h>
>>>> +#include <linux/libfdt.h>
>>>> +#include <linux/of_fdt.h>
>>>> +
>>>> +#include <asm/bootinfo.h>
>>>> +#include <asm/cacheflush.h>
>>>> +#include <asm/page.h>
>>>> +
>>>> +/* 0x100000 ~ 0x200000 is safe */
>>>> +#define KEXEC_CTRL_CODE    TO_CACHE(0x100000UL)
>>>> +#define KEXEC_BLOB_ADDR    TO_CACHE(0x108000UL)
>>>> +
>>>> +static unsigned long reboot_code_buffer;
>>>> +#ifdef CONFIG_SMP
>>>> +void (*relocated_kexec_smp_wait)(void *);
>>>> +atomic_t kexec_ready_to_reboot = ATOMIC_INIT(0);
>>>> +#endif
>>>> +
>>>> +static unsigned long jump_addr;
>>>> +static unsigned long first_ind_entry;
>>>> +static unsigned long boot_flag;
>>>> +static unsigned long fdt_addr;
>>>> +
>>>> +static void kexec_image_info(const struct kimage *kimage)
>>>> +{
>>>> +    unsigned long i;
>>>> +
>>>> +    pr_debug("kexec kimage info:\n");
>>>> +    pr_debug("\ttype:        %d\n", kimage->type);
>>>> +    pr_debug("\tstart:       %lx\n", kimage->start);
>>>> +    pr_debug("\thead:        %lx\n", kimage->head);
>>>> +    pr_debug("\tnr_segments: %lu\n", kimage->nr_segments);
>>>> +
>>>> +    for (i = 0; i < kimage->nr_segments; i++) {
>>>> +        pr_debug("\t    segment[%lu]: %016lx - %016lx", i,
>>>> +            kimage->segment[i].mem,
>>>> +            kimage->segment[i].mem + kimage->segment[i].memsz);
>>>> +        pr_debug("\t\t0x%lx bytes, %lu pages\n",
>>>> +            (unsigned long)kimage->segment[i].memsz,
>>>> +            (unsigned long)kimage->segment[i].memsz /  PAGE_SIZE);
>>>> +    }
>>>> +}
>>>> +
>>>> +int machine_kexec_prepare(struct kimage *kimage)
>>>> +{
>>>> +    int i;
>>>> +    void *dtb = (void *)KEXEC_BLOB_ADDR;
>>>> +
>>>> +    kexec_image_info(kimage);
>>>> +
>>>> +    /* Find the Flattened Device Tree */
>>>> +    for (i = 0; i < kimage->nr_segments; i++) {
>>>> +        if (!fdt_check_header(kimage->segment[i].buf)) {
>>>> +            memcpy(dtb, kimage->segment[i].buf, SZ_64K);
>>>> +            kimage->arch.boot_flag = fw_arg0;
>>>> +            kimage->arch.fdt_addr = (unsigned long) dtb;
>>>> +            break;
>>>> +        }
>>>> +        continue;
>>>> +    }
>>>> +
>>>> +    /* kexec need a safe page to save reboot_code_buffer */
>>>> +    kimage->control_code_page = virt_to_page((void *)KEXEC_CTRL_CODE);
>>>> +
>>>> +    reboot_code_buffer =
>>>> +      (unsigned long)page_address(kimage->control_code_page);
>>>> +    memcpy((void *)reboot_code_buffer, relocate_new_kernel,
>>>> +           relocate_new_kernel_size);
>>> It copys same content to KEXEC_CTRL_CODE each time, could we do this at
>>> boot time?
>> I think it's possible to have the copy action happen at boot-time or
>> during the prepare phase. (RISCV in prepare, MIPS in boot-time)
>>
>>> BTW, our system always keep the low-2MB no used, on mips-loongson or
>>> LoongArch. Is that necessary on LoongArch? We cannot use parameter
>>> 'mem=YYM' normally but 'mem=YYM@2M' is ok. And the low-2MB is not
>>> in virtual memory management, although we can get it in kernel.
>> For existing kernels, the low 2M has been reserved by
>> memblock_reserve(PHYS_OFFSET, 0x200000), maybe it is acceptable to keep
>> the low 2M behavior.
>>
>> Yes, we need to use "mem=YM@2M" if the low 2M is reserved.
>>
>>> In kexec/kdump process, we can follows kimage_alloc_control_pages().
>>> When the boot cpu copy complete the second-kernels, all cpus can jump
>>> to a kernel-entry-trampoline which is in kernel image. Then we don't
>>> worry about the code can be destroyed. The kernel-entry-trampoline
>>> get its cpuid, keep non-boot cpus do as kexec_smp_wait and let boot
>>> cpu go kernel-entry. In this way we can drop the low-2MB IMO.
>> It is also feasible to dynamically allocate control pages, but it is
>> easier to use a low 2M approach. What do you think, Huacai?
> I prefer to use the low 2MB.
>
> Huacai
Low 2MB also is ok for me, like a trick. And should it free
control_code_page here?

>>>> +
>>>> +    /* All secondary cpus now may jump to kexec_smp_wait cycle */
>>>> +    relocated_kexec_smp_wait = reboot_code_buffer +
>>>> +        (void *)(kexec_smp_wait - relocate_new_kernel);
>>>> +
>>>> +    return 0;
>>>> +}
>>>> +
>>>> +void machine_kexec_cleanup(struct kimage *kimage)
>>>> +{
>>>> +}
>>>> +
>>>> +#ifdef CONFIG_SMP
>>>> +void kexec_reboot(void)
>>>> +{
>>>> +    do_kexec_t do_kexec = NULL;
>>>> +
>>>> +    /* All secondary cpus go to kexec_smp_wait */
>>>> +    if (smp_processor_id() > 0) {
>>>> +        relocated_kexec_smp_wait(NULL);
>>>> +        unreachable();
>>>> +    }
>>>> +
>>>> +    do_kexec = (void *)reboot_code_buffer;
>>>> +    do_kexec(boot_flag, fdt_addr, first_ind_entry, jump_addr);
>>>> +
>>>> +    unreachable();
>>>> +}
>>>> +
>>>> +static void kexec_shutdown_secondary(void *)
>>>> +{
>>>> +    local_irq_disable();
>>>> +    while (!atomic_read(&kexec_ready_to_reboot))
>>>> +        cpu_relax();
>>>> +
>>>> +    kexec_reboot();
>>>> +}
>>>> +
>>>> +void machine_crash_shutdown(struct pt_regs *regs)
>>>> +{
>>>> +}
>>>> +#endif
>>>> +
>>>> +void machine_shutdown(void)
>>>> +{
>>>> +    smp_call_function(kexec_shutdown_secondary, NULL, 0);
>>>> +}
>>>> +
>>>> +void machine_kexec(struct kimage *image)
>>>> +{
>>>> +    unsigned long entry;
>>>> +    unsigned long *ptr;
>>>> +    struct kimage_arch *internal = &image->arch;
>>>> +
>>>> +    boot_flag = internal->boot_flag;
>>>> +    fdt_addr = internal->fdt_addr;
>>>> +
>>>> +    jump_addr = (unsigned long)phys_to_virt(image->start);
>>>> +
>>>> +    first_ind_entry = (unsigned long)phys_to_virt(image->head &
>>>> PAGE_MASK);
>>>> +
>>>> +    /*
>>>> +     * The generic kexec code builds a page list with physical
>>>> +     * addresses. they are directly accessible through XKPRANGE
>>>> +     * hence the phys_to_virt() call.
>>>> +     */
>>>> +    for (ptr = &image->head; (entry = *ptr) && !(entry & IND_DONE);
>>>> +         ptr = (entry & IND_INDIRECTION) ?
>>>> +           phys_to_virt(entry & PAGE_MASK) : ptr + 1) {
>>>> +        if (*ptr & IND_SOURCE || *ptr & IND_INDIRECTION ||
>>>> +            *ptr & IND_DESTINATION)
>>>> +            *ptr = (unsigned long) phys_to_virt(*ptr);
>>>> +    }
>>>> +
>>>> +    /* Mark offline before disabling local irq. */
>>>> +    set_cpu_online(smp_processor_id(), false);
>>>> +
>>>> +    /* we do not want to be bothered. */
>>>> +    local_irq_disable();
>>>> +
>>>> +    pr_notice("Will call new kernel at %lx\n", jump_addr);
>>>> +    pr_notice("FDT image at %lx\n", fdt_addr);
>>>> +    pr_notice("Bye ...\n");
>>>> +
>>>> +    /* Make reboot code buffer available to the boot CPU. */
>>>> +    flush_cache_all();
>>>> +
>>>> +    atomic_set(&kexec_ready_to_reboot, 1);
>>>> +
>>>> +    /*
>>>> +     * We know we were online, and there will be no incoming IPIs at
>>>> +     * this point.
>>>> +     */
>>>> +    set_cpu_online(smp_processor_id(), true);
>>>> +
>>>> +    /* Ensure remote CPUs observe that we're online before rebooting. */
>>>> +    smp_mb__after_atomic();
>>>> +
>>>> +    kexec_reboot();
>>>> +}
>>>> diff --git a/arch/loongarch/kernel/relocate_kernel.S
>>>> b/arch/loongarch/kernel/relocate_kernel.S
>>>> new file mode 100644
>>>> index 000000000000..d1f242f74ea8
>>>> --- /dev/null
>>>> +++ b/arch/loongarch/kernel/relocate_kernel.S
>>>> @@ -0,0 +1,125 @@
>>>> +/* SPDX-License-Identifier: GPL-2.0 */
>>>> +/*
>>>> + * relocate_kernel.S for kexec
>>>> + *
>>>> + * Copyright (C) 2022 Loongson Technology Corporation Limited
>>>> + */
>>>> +
>>>> +#include <linux/kexec.h>
>>>> +
>>>> +#include <asm/asm.h>
>>>> +#include <asm/asmmacro.h>
>>>> +#include <asm/regdef.h>
>>>> +#include <asm/loongarch.h>
>>>> +#include <asm/stackframe.h>
>>>> +#include <asm/addrspace.h>
>>>> +
>>>> +#define IPI_REG_BASE 0x1fe01000
>>>> +
>>>> +SYM_CODE_START(relocate_new_kernel)
>>>> +    /*
>>>> +     * s0: Boot flag passed to the new kernel
>>>> +     * s1: Virt address of the FDT image
>>>> +     * s2: Pointer to the current entry
>>>> +     * s3: Virt address to jump to after relocation
>>>> +     */
>>>> +    move        s0, a0
>>>> +    move        s1, a1
>>>> +    move        s2, a2
>>>> +    move        s3, a3
>>>> +
>>>> +process_entry:
>>>> +    PTR_L        s4, s2, 0
>>>> +    PTR_ADDI    s2, s2, SZREG
>>>> +
>>>> +    /* destination page */
>>>> +    andi        s5, s4, IND_DESTINATION
>>>> +    beqz        s5, 1f
>>>> +    li.w        t0, ~0x1
>>>> +    and        s6, s4, t0    /* store destination addr in s6 */
>>>> +    b        process_entry
>>>> +
>>>> +1:
>>>> +    /* indirection page, update s2    */
>>>> +    andi        s5, s4, IND_INDIRECTION
>>>> +    beqz        s5, 1f
>>>> +    li.w        t0, ~0x2
>>>> +    and        s2, s4, t0
>>>> +    b        process_entry
>>>> +
>>>> +1:
>>>> +    /* done page */
>>>> +    andi        s5, s4, IND_DONE
>>>> +    beqz        s5, 1f
>>>> +    b        done
>>>> +1:
>>>> +    /* source page */
>>>> +    andi        s5, s4, IND_SOURCE
>>>> +    beqz        s5, process_entry
>>>> +    li.w        t0, ~0x8
>>>> +    and        s4, s4, t0
>>>> +    li.w        s8, (1 << _PAGE_SHIFT) / SZREG
>>>> +
>>>> +copy_word:
>>>> +    /* copy page word by word */
>>>> +    REG_L        s7, s4, 0
>>>> +    REG_S        s7, s6, 0
>>>> +    PTR_ADDI    s6, s6, SZREG
>>>> +    PTR_ADDI    s4, s4, SZREG
>>>> +    LONG_ADDI    s8, s8, -1
>>>> +    beqz        s8, process_entry
>>>> +    b        copy_word
>>>> +    b        process_entry
>>>> +
>>>> +done:
>>>> +    dbar        0
>>> ibar, too?
>> Will add ibar 0.
>>
>>>> +
>>>> +    move        a0, s0
>>>> +    move        a1, s1
>>>> +    /* jump to the new kernel */
>>>> +    jr        s3
>>>> +SYM_CODE_END(relocate_new_kernel)
>>>> +
>>>> +#ifdef CONFIG_SMP
>>>> +/*
>>>> + * Other CPUs should wait until code is relocated and
>>>> + * then start at entry (?) point.
>>>> + */
>>>> +SYM_CODE_START(kexec_smp_wait)
>>>> +    li.d        t0, IPI_REG_BASE
>>>> +    li.d        t1, UNCACHE_BASE
>>>> +    or        t0, t0, t1
>>>> +
>>>> +    /*
>>>> +     * s1:initfn
>>>> +     * t0:base t1:cpuid t2:node t3:core t4:count
>>>> +     */
>>>> +    csrrd        t1, LOONGARCH_CSR_CPUID
>>>> +    andi        t1, t1, CSR_CPUID_COREID
>>>> +    andi        t3, t1, 0x3
>>>> +    slli.w        t3, t3, 8              /* get core id */
>>>> +    or        t0, t0, t3
>>>> +    andi        t2, t1, 0x3c
>>>> +    slli.d        t2, t2, 42             /* get node id */
>>>> +    or        t0, t0, t2
>>>> +
>>>> +1:    li.w        t4, 0x100              /* wait for init loop */
>>>> +2:    addi.w        t4, t4, -1             /* limit mailbox access */
>>>> +    bnez        t4, 2b
>>>> +    ld.w        s1, t0, 0x20           /* check PC as an indicator */
>>> Can we do this with iocsr*?
>> OK, I will consider the implementation in the iocsr way.
>>
>> Thanks,
>> Youling
>>> Thanks,
>>> Jinyang
>>>> +    beqz        s1, 1b
>>>> +    ld.d        s1, t0, 0x20           /* get PC via mailbox */
>>>> +    ld.d        sp, t0, 0x28           /* get SP via mailbox */
>>>> +    ld.d        tp, t0, 0x30           /* get TP via mailbox */
>>>> +
>>>> +    li.d        t0, CACHE_BASE
>>>> +    or        s1, s1, t0
>>>> +    jr        s1                     /* jump to initial PC */
>>>> +SYM_CODE_END(kexec_smp_wait)
>>>> +#endif
>>>> +
>>>> +relocate_new_kernel_end:
>>>> +
>>>> +SYM_DATA_START(relocate_new_kernel_size)
>>>> +    PTR        relocate_new_kernel_end - relocate_new_kernel
>>>> +SYM_DATA_END(relocate_new_kernel_size)

[PATCH 1/3] LoongArch: Add kexec support
[PATCH 2/3] LoongArch: Add kdump support
[PATCH 3/3] LoongArch: Enable CONFIG_KEXEC