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Date: Fri, 9 Sep 2022 16:16:08 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Youling Tang <tangyouling@...ngson.cn>
Cc: Baoquan He <bhe@...hat.com>,
Eric Biederman <ebiederm@...ssion.com>,
WANG Xuerui <kernel@...0n.name>,
Vivek Goyal <vgoyal@...hat.com>,
Dave Young <dyoung@...hat.com>, Guo Ren <guoren@...nel.org>,
Jiaxun Yang <jiaxun.yang@...goat.com>,
Jinyang He <hejinyang@...ngson.cn>, kexec@...ts.infradead.org,
loongarch@...ts.linux.dev, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] LoongArch: Add kexec support
Hi, Youling,
On Fri, Sep 9, 2022 at 11:20 AM Youling Tang <tangyouling@...ngson.cn> 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@...ngson.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 | 188 ++++++++++++++++++++++++
> arch/loongarch/kernel/relocate_kernel.S | 106 +++++++++++++
> 6 files changed, 371 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 9b1f2ab878e9..08e063aaf847 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -422,6 +422,17 @@ config ARCH_IOREMAP
> protection support. However, you can enable LoongArch DMW-based
> ioremap() for better performance.
>
> +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..f23506725e00
> --- /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;
> +};
I prefer to change boot_flag to efi_boot, the latter is better to
correspond the current usage, and keeps consistency with efistub.
> +
> +typedef void (*do_kexec_t)(unsigned long boot_flag,
> + unsigned long fdt_addr,
> + unsigned long first_ind_entry,
> + unsigned long jump_addr);
I prefer change the order of jump_addr and first_ind_entry here.
> +
> +struct kimage;
> +extern const unsigned char relocate_new_kernel[];
> +extern const size_t relocate_new_kernel_size;
> +extern void kexec_reboot(void);
> +
> +#ifdef CONFIG_SMP
> +extern atomic_t kexec_ready_to_reboot;
> +extern const unsigned char kexec_smp_wait[];
> +#endif
> +
> +#endif /* !_ASM_KEXEC_H */
> diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
> index 7225916dd378..17dc8ce6b5ce 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 eb3f641d5915..0f786d670e66 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 */
As discussed before, I prefer kernel entry point before kernel image size.
>
> pe_header:
> diff --git a/arch/loongarch/kernel/machine_kexec.c b/arch/loongarch/kernel/machine_kexec.c
> new file mode 100644
> index 000000000000..7b3fea506c6d
> --- /dev/null
> +++ b/arch/loongarch/kernel/machine_kexec.c
> @@ -0,0 +1,188 @@
> +// 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
> +static 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;
Keep the same order as do_kexec() may be better.
> +
> +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);
> +
> +#ifdef CONFIG_SMP
> + /* 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);
> +#endif
> +
> + return 0;
> +}
> +
> +void machine_kexec_cleanup(struct kimage *kimage)
> +{
> +}
> +
> +void kexec_reboot(void)
> +{
> + do_kexec_t do_kexec = NULL;
> +
The old implementation has an "ibar" here, I suppose it is still needed?
> +#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();
> +}
> +
> +
> +#ifdef CONFIG_SMP
> +static void kexec_shutdown_secondary(void *)
> +{
> + local_irq_disable();
> + while (!atomic_read(&kexec_ready_to_reboot))
> + cpu_relax();
> +
> + kexec_reboot();
The old implementation has an unreachable() after kexec_reboot(), but
I don't know whether it is really needed.
> +}
> +#endif
> +
> +void machine_crash_shutdown(struct pt_regs *regs)
> +{
> +}
> +
> +void machine_shutdown(void)
> +{
> +#ifdef CONFIG_SMP
> + smp_call_function(kexec_shutdown_secondary, NULL, 0);
> +#endif
> +}
> +
> +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();
> +
> +#ifdef CONFIG_SMP
> + atomic_set(&kexec_ready_to_reboot, 1);
> +#endif
> +
> + /*
> + * 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..05a0c1ccfab6
> --- /dev/null
> +++ b/arch/loongarch/kernel/relocate_kernel.S
> @@ -0,0 +1,106 @@
> +/* 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>
> +
> +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
"Pointer to the current entry" can be "Pointer to the current
indirection page entry"? And I think we needn't backup Ax to Sx except
this one in the assembly below.
Huacai
> + * 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:
> + ibar 0
> + 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)
> +1: li.w t0, 0x100 /* wait for init loop */
> +2: addi.w t0, t0, -1 /* limit mailbox access */
> + bnez t0, 2b
> + li.w t1, LOONGARCH_IOCSR_MBUF0
> + iocsrrd.w s1, t1 /* check PC as an indicator */
> + beqz s1, 1b
> + iocsrrd.d s1, t1 /* get PC via mailbox */
> +
> + li.d t0, CACHE_BASE
> + or s1, s1, t0 /* s1 = TO_CACHE(s1) */
> + 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
>
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