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    SubjectRe: [PATCH 1/3] LoongArch: Add kexec support
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    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)
    >

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      Last update: 2022-08-30 05:26    [W:2.775 / U:0.092 seconds]
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