Re: [PATCH 2/3] LoongArch: Add kdump support

From: Huacai Chen
Date: Sun Sep 04 2022 - 22:14:40 EST

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On Mon, Sep 5, 2022 at 10:04 AM Youling Tang <tangyouling@xxxxxxxxxxx> wrote:
>
> Hi, Huacai
>
> On 09/05/2022 09:38 AM, Huacai Chen wrote:
> > Hi, Youling,
> >
> > On Mon, Sep 5, 2022 at 8:54 AM Youling Tang <tangyouling@xxxxxxxxxxx> wrote:
> >>
> >> Hi, Huacai
> >>
> >> On 09/04/2022 08:21 PM, Huacai Chen wrote:
> >>> Hi, Youling,
> >>>
> >>> I think crash.c can be merged into crash_dump.c
> >>
> >> Most architectures only implement copy_oldmem_page() in crash_dump.c,
> >> I'm not sure if merging crash.c into crash_dump.c will break its
> >> consistency?
> >>
> >> Thanks,
> >> Youling
> > Yes, you are right, crash.c cannot be merged into crash_dump.c, but it
> > can be merged into machine_kexec.c, as arm64 and riscv do.
>
> For arm64, machine_crash_shutdown() is placed in machine_kexec.c, and
> crash_smp_send_stop is placed in smp.c. If crash.c needs to be merged
> into machine_kexec.c, should crash_shutdown_secondary and
> crash_smp_send_stop be placed in smp.c?
I don't want to touch smp.c, all merged into machine_kexec.c seems reasonable.

Huacai
>
> Youling.
> >
> > Huacai
> >>
> >>>
> >>> Huacai
> >>>
> >>> On Mon, Aug 29, 2022 at 12:37 PM Youling Tang <tangyouling@xxxxxxxxxxx> wrote:
> >>>>
> >>>> This patch adds support for kdump, the kernel will reserve a region
> >>>> for the crash kernel and jump there on panic.
> >>>>
> >>>> Arch-specific functions are added to allow for implementing a crash
> >>>> dump file interface, /proc/vmcore, which can be viewed as a ELF file.
> >>>>
> >>>> A user space tool, like kexec-tools, is responsible for allocating a
> >>>> separate region for the core's ELF header within crash kdump kernel
> >>>> memory and filling it in when executing kexec_load().
> >>>>
> >>>> Then, its location will be advertised to crash dump kernel via a new
> >>>> device-tree property, "linux,elfcorehdr", and crash dump kernel preserves
> >>>> the region for later use with fdt_reserve_elfcorehdr() at boot time.
> >>>>
> >>>> At the same time, it will also limit the crash kdump kernel to the
> >>>> crashkernel area via a new device-tree property, "linux, usable-memory-range",
> >>>> so as not to destroy the original kernel dump data.
> >>>>
> >>>> On crash dump kernel, /proc/vmcore will access the primary kernel's memory
> >>>> with copy_oldmem_page().
> >>>>
> >>>> I tested this on LoongArch 3A5000 machine and works as expected (Suggest
> >>>> crashkernel parameter is "crashkernel=512M@2320M"), you may test it by
> >>>> triggering a crash through /proc/sysrq_trigger:
> >>>>
> >>>> $ sudo kexec -p /boot/vmlinux-kdump --reuse-cmdline --append="nr_cpus=1"
> >>>> # echo c > /proc/sysrq_trigger
> >>>>
> >>>> Signed-off-by: Youling Tang <tangyouling@xxxxxxxxxxx>
> >>>> ---
> >>>> arch/loongarch/Kconfig | 22 ++++++
> >>>> arch/loongarch/Makefile | 4 +
> >>>> arch/loongarch/kernel/Makefile | 3 +-
> >>>> arch/loongarch/kernel/crash.c | 100 ++++++++++++++++++++++++
> >>>> arch/loongarch/kernel/crash_dump.c | 19 +++++
> >>>> arch/loongarch/kernel/machine_kexec.c | 12 ++-
> >>>> arch/loongarch/kernel/mem.c | 6 ++
> >>>> arch/loongarch/kernel/relocate_kernel.S | 6 ++
> >>>> arch/loongarch/kernel/setup.c | 49 ++++++++++++
> >>>> arch/loongarch/kernel/traps.c | 4 +
> >>>> 10 files changed, 217 insertions(+), 8 deletions(-)
> >>>> create mode 100644 arch/loongarch/kernel/crash.c
> >>>> create mode 100644 arch/loongarch/kernel/crash_dump.c
> >>>>
> >>>> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> >>>> index 903c82fa958d..7c1b07a5b5bd 100644
> >>>> --- a/arch/loongarch/Kconfig
> >>>> +++ b/arch/loongarch/Kconfig
> >>>> @@ -420,6 +420,28 @@ config KEXEC
> >>>>
> >>>> The name comes from the similarity to the exec system call.
> >>>>
> >>>> +config CRASH_DUMP
> >>>> + bool "Build kdump crash kernel"
> >>>> + help
> >>>> + Generate crash dump after being started by kexec. This should
> >>>> + be normally only set in special crash dump kernels which are
> >>>> + loaded in the main kernel with kexec-tools into a specially
> >>>> + reserved region and then later executed after a crash by
> >>>> + kdump/kexec.
> >>>> +
> >>>> + For more details see Documentation/admin-guide/kdump/kdump.rst
> >>>> +
> >>>> +config PHYSICAL_START
> >>>> + hex "Physical address where the kernel is loaded"
> >>>> + default "0x9000000091000000" if 64BIT
> >>>> + depends on CRASH_DUMP
> >>>> + help
> >>>> + This gives the XKPRANGE address where the kernel is loaded.
> >>>> + If you plan to use kernel for capturing the crash dump change
> >>>> + this value to start of the reserved region (the "X" value as
> >>>> + specified in the "crashkernel=YM@XM" command line boot parameter
> >>>> + passed to the panic-ed kernel).
> >>>> +
> >>>> config SECCOMP
> >>>> bool "Enable seccomp to safely compute untrusted bytecode"
> >>>> depends on PROC_FS
> >>>> diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile
> >>>> index 4bc47f47cfd8..7dabd580426d 100644
> >>>> --- a/arch/loongarch/Makefile
> >>>> +++ b/arch/loongarch/Makefile
> >>>> @@ -48,7 +48,11 @@ KBUILD_CFLAGS_MODULE += -fplt -Wa,-mla-global-with-abs,-mla-local-with-abs
> >>>> cflags-y += -ffreestanding
> >>>> cflags-y += $(call cc-option, -mno-check-zero-division)
> >>>>
> >>>> +ifdef CONFIG_PHYSICAL_START
> >>>> +load-y = $(CONFIG_PHYSICAL_START)
> >>>> +else
> >>>> load-y = 0x9000000000200000
> >>>> +endif
> >>>> bootvars-y = VMLINUX_LOAD_ADDRESS=$(load-y)
> >>>>
> >>>> drivers-$(CONFIG_PCI) += arch/loongarch/pci/
> >>>> diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
> >>>> index 20b64ac3f128..df5aea129364 100644
> >>>> --- a/arch/loongarch/kernel/Makefile
> >>>> +++ b/arch/loongarch/kernel/Makefile
> >>>> @@ -17,7 +17,8 @@ obj-$(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_KEXEC) += machine_kexec.o relocate_kernel.o crash.o
> >>>> +obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
> >>>>
> >>>> obj-$(CONFIG_PROC_FS) += proc.o
> >>>>
> >>>> diff --git a/arch/loongarch/kernel/crash.c b/arch/loongarch/kernel/crash.c
> >>>> new file mode 100644
> >>>> index 000000000000..b4f249ec6301
> >>>> --- /dev/null
> >>>> +++ b/arch/loongarch/kernel/crash.c
> >>>> @@ -0,0 +1,100 @@
> >>>> +// SPDX-License-Identifier: GPL-2.0
> >>>> +/*
> >>>> + * Copyright (C) 2022 Loongson Technology Corporation Limited
> >>>> + *
> >>>> + * Derived from MIPS
> >>>> + */
> >>>> +#include <linux/kernel.h>
> >>>> +#include <linux/smp.h>
> >>>> +#include <linux/reboot.h>
> >>>> +#include <linux/crash_dump.h>
> >>>> +#include <linux/delay.h>
> >>>> +#include <linux/irq.h>
> >>>> +#include <linux/types.h>
> >>>> +#include <linux/sched.h>
> >>>> +#include <linux/sched/task_stack.h>
> >>>> +#include <asm/cacheflush.h>
> >>>> +#include <asm/kexec.h>
> >>>> +
> >>>> +static cpumask_t cpus_in_crash = CPU_MASK_NONE;
> >>>> +
> >>>> +#ifdef CONFIG_SMP
> >>>> +static void crash_shutdown_secondary(void *passed_regs)
> >>>> +{
> >>>> + struct pt_regs *regs = passed_regs;
> >>>> + int cpu = smp_processor_id();
> >>>> +
> >>>> + /*
> >>>> + * If we are passed registers, use those. Otherwise get the
> >>>> + * regs from the last interrupt, which should be correct, as
> >>>> + * we are in an interrupt. But if the regs are not there,
> >>>> + * pull them from the top of the stack. They are probably
> >>>> + * wrong, but we need something to keep from crashing again.
> >>>> + */
> >>>> + if (!regs)
> >>>> + regs = get_irq_regs();
> >>>> + if (!regs)
> >>>> + regs = task_pt_regs(current);
> >>>> +
> >>>> + local_irq_disable();
> >>>> + if (!cpumask_test_cpu(cpu, &cpus_in_crash))
> >>>> + crash_save_cpu(regs, cpu);
> >>>> + cpumask_set_cpu(cpu, &cpus_in_crash);
> >>>> +
> >>>> + while (!atomic_read(&kexec_ready_to_reboot))
> >>>> + cpu_relax();
> >>>> +
> >>>> + kexec_reboot();
> >>>> +}
> >>>> +
> >>>> +/* Override the weak function in kernel/panic.c */
> >>>> +void crash_smp_send_stop(void)
> >>>> +{
> >>>> + static int cpus_stopped;
> >>>> + unsigned long timeout;
> >>>> + unsigned int ncpus;
> >>>> +
> >>>> + /*
> >>>> + * This function can be called twice in panic path, but obviously
> >>>> + * we execute this only once.
> >>>> + */
> >>>> + if (cpus_stopped)
> >>>> + return;
> >>>> +
> >>>> + cpus_stopped = 1;
> >>>> +
> >>>> + /* Excluding the panic cpu */
> >>>> + ncpus = num_online_cpus() - 1;
> >>>> +
> >>>> + smp_call_function(crash_shutdown_secondary, NULL, 0);
> >>>> + smp_wmb();
> >>>> +
> >>>> + /*
> >>>> + * The crash CPU sends an IPI and wait for other CPUs to
> >>>> + * respond. Delay of at least 10 seconds.
> >>>> + */
> >>>> + pr_emerg("Sending IPI to other cpus...\n");
> >>>> + timeout = USEC_PER_SEC * 10;
> >>>> + while ((cpumask_weight(&cpus_in_crash) < ncpus) && timeout--) {
> >>>> + cpu_relax();
> >>>> + udelay(1);
> >>>> + }
> >>>> +}
> >>>> +
> >>>> +#endif
> >>>> +
> >>>> +void machine_crash_shutdown(struct pt_regs *regs)
> >>>> +{
> >>>> + int crashing_cpu;
> >>>> +
> >>>> + local_irq_disable();
> >>>> +
> >>>> + crashing_cpu = smp_processor_id();
> >>>> + crash_save_cpu(regs, crashing_cpu);
> >>>> +
> >>>> + /* shutdown non-crashing cpus */
> >>>> + crash_smp_send_stop();
> >>>> + cpumask_set_cpu(crashing_cpu, &cpus_in_crash);
> >>>> +
> >>>> + pr_info("Starting crashdump kernel...\n");
> >>>> +}
> >>>> diff --git a/arch/loongarch/kernel/crash_dump.c b/arch/loongarch/kernel/crash_dump.c
> >>>> new file mode 100644
> >>>> index 000000000000..13e5d2f7870d
> >>>> --- /dev/null
> >>>> +++ b/arch/loongarch/kernel/crash_dump.c
> >>>> @@ -0,0 +1,19 @@
> >>>> +// SPDX-License-Identifier: GPL-2.0
> >>>> +#include <linux/highmem.h>
> >>>> +#include <linux/crash_dump.h>
> >>>> +#include <linux/io.h>
> >>>> +
> >>>> +ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
> >>>> + size_t csize, unsigned long offset)
> >>>> +{
> >>>> + void *vaddr;
> >>>> +
> >>>> + if (!csize)
> >>>> + return 0;
> >>>> +
> >>>> + vaddr = kmap_local_pfn(pfn);
> >>>> + csize = copy_to_iter(vaddr + offset, csize, iter);
> >>>> + kunmap_local(vaddr);
> >>>> +
> >>>> + return csize;
> >>>> +}
> >>>> diff --git a/arch/loongarch/kernel/machine_kexec.c b/arch/loongarch/kernel/machine_kexec.c
> >>>> index 4ffcd4cd9c8c..f793a3ff09a3 100644
> >>>> --- a/arch/loongarch/kernel/machine_kexec.c
> >>>> +++ b/arch/loongarch/kernel/machine_kexec.c
> >>>> @@ -69,7 +69,7 @@ int machine_kexec_prepare(struct kimage *kimage)
> >>>> continue;
> >>>> }
> >>>>
> >>>> - /* kexec need a safe page to save reboot_code_buffer */
> >>>> + /* kexec/kdump need a safe page to save reboot_code_buffer */
> >>>> kimage->control_code_page = virt_to_page((void *)KEXEC_CTRL_CODE);
> >>>>
> >>>> reboot_code_buffer =
> >>>> @@ -113,10 +113,6 @@ static void kexec_shutdown_secondary(void *)
> >>>>
> >>>> kexec_reboot();
> >>>> }
> >>>> -
> >>>> -void machine_crash_shutdown(struct pt_regs *regs)
> >>>> -{
> >>>> -}
> >>>> #endif
> >>>>
> >>>> void machine_shutdown(void)
> >>>> @@ -135,7 +131,8 @@ void machine_kexec(struct kimage *image)
> >>>>
> >>>> jump_addr = (unsigned long)phys_to_virt(image->start);
> >>>>
> >>>> - first_ind_entry = (unsigned long)phys_to_virt(image->head & PAGE_MASK);
> >>>> + if (image->type == KEXEC_TYPE_DEFAULT)
> >>>> + first_ind_entry = (unsigned long)phys_to_virt(image->head & PAGE_MASK);
> >>>>
> >>>> /*
> >>>> * The generic kexec code builds a page list with physical
> >>>> @@ -167,7 +164,8 @@ void machine_kexec(struct kimage *image)
> >>>>
> >>>> /*
> >>>> * We know we were online, and there will be no incoming IPIs at
> >>>> - * this point.
> >>>> + * this point. Mark online again before rebooting so that the crash
> >>>> + * analysis tool will see us correctly.
> >>>> */
> >>>> set_cpu_online(smp_processor_id(), true);
> >>>>
> >>>> diff --git a/arch/loongarch/kernel/mem.c b/arch/loongarch/kernel/mem.c
> >>>> index 7423361b0ebc..c6def6ff81c8 100644
> >>>> --- a/arch/loongarch/kernel/mem.c
> >>>> +++ b/arch/loongarch/kernel/mem.c
> >>>> @@ -5,6 +5,7 @@
> >>>> #include <linux/efi.h>
> >>>> #include <linux/initrd.h>
> >>>> #include <linux/memblock.h>
> >>>> +#include <linux/of_fdt.h>
> >>>>
> >>>> #include <asm/bootinfo.h>
> >>>> #include <asm/loongson.h>
> >>>> @@ -61,4 +62,9 @@ void __init memblock_init(void)
> >>>>
> >>>> /* Reserve the initrd */
> >>>> reserve_initrd_mem();
> >>>> +
> >>>> + /* Mainly reserved memory for the elf core head */
> >>>> + early_init_fdt_scan_reserved_mem();
> >>>> + /* Parse linux,usable-memory-range is for crash dump kernel */
> >>>> + early_init_dt_check_for_usable_mem_range();
> >>>> }
> >>>> diff --git a/arch/loongarch/kernel/relocate_kernel.S b/arch/loongarch/kernel/relocate_kernel.S
> >>>> index d1f242f74ea8..4ee5ac4ac2d7 100644
> >>>> --- a/arch/loongarch/kernel/relocate_kernel.S
> >>>> +++ b/arch/loongarch/kernel/relocate_kernel.S
> >>>> @@ -28,6 +28,12 @@ SYM_CODE_START(relocate_new_kernel)
> >>>> move s2, a2
> >>>> move s3, a3
> >>>>
> >>>> + /*
> >>>> + * In case of a kdump/crash kernel, the indirection page is not
> >>>> + * populated as the kernel is directly copied to a reserved location
> >>>> + */
> >>>> + beqz s2, done
> >>>> +
> >>>> process_entry:
> >>>> PTR_L s4, s2, 0
> >>>> PTR_ADDI s2, s2, SZREG
> >>>> diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
> >>>> index f938aae3e92c..ea34b77e402f 100644
> >>>> --- a/arch/loongarch/kernel/setup.c
> >>>> +++ b/arch/loongarch/kernel/setup.c
> >>>> @@ -19,6 +19,8 @@
> >>>> #include <linux/memblock.h>
> >>>> #include <linux/initrd.h>
> >>>> #include <linux/ioport.h>
> >>>> +#include <linux/kexec.h>
> >>>> +#include <linux/crash_dump.h>
> >>>> #include <linux/root_dev.h>
> >>>> #include <linux/console.h>
> >>>> #include <linux/pfn.h>
> >>>> @@ -186,6 +188,50 @@ static int __init early_parse_mem(char *p)
> >>>> }
> >>>> early_param("mem", early_parse_mem);
> >>>>
> >>>> +static void __init loongarch_parse_crashkernel(void)
> >>>> +{
> >>>> +#ifdef CONFIG_KEXEC
> >>>> + unsigned long long start;
> >>>> + unsigned long long total_mem;
> >>>> + unsigned long long crash_size, crash_base;
> >>>> + int ret;
> >>>> +
> >>>> + total_mem = memblock_phys_mem_size();
> >>>> + ret = parse_crashkernel(boot_command_line, total_mem,
> >>>> + &crash_size, &crash_base);
> >>>> + if (ret != 0 || crash_size <= 0)
> >>>> + return;
> >>>> +
> >>>> +
> >>>> + start = memblock_phys_alloc_range(crash_size, 1, crash_base,
> >>>> + crash_base + crash_size);
> >>>> + if (start != crash_base) {
> >>>> + pr_warn("Invalid memory region reserved for crash kernel\n");
> >>>> + return;
> >>>> + }
> >>>> +
> >>>> + crashk_res.start = crash_base;
> >>>> + crashk_res.end = crash_base + crash_size - 1;
> >>>> +#endif
> >>>> +}
> >>>> +
> >>>> +static void __init request_crashkernel(struct resource *res)
> >>>> +{
> >>>> +#ifdef CONFIG_KEXEC
> >>>> + int ret;
> >>>> +
> >>>> + if (crashk_res.start == crashk_res.end)
> >>>> + return;
> >>>> +
> >>>> + ret = request_resource(res, &crashk_res);
> >>>> + if (!ret)
> >>>> + pr_info("Reserving %ldMB of memory at %ldMB for crashkernel\n",
> >>>> + (unsigned long)((crashk_res.end -
> >>>> + crashk_res.start + 1) >> 20),
> >>>> + (unsigned long)(crashk_res.start >> 20));
> >>>> +#endif
> >>>> +}
> >>>> +
> >>>> void __init platform_init(void)
> >>>> {
> >>>> efi_init();
> >>>> @@ -229,6 +275,8 @@ static void __init arch_mem_init(char **cmdline_p)
> >>>>
> >>>> check_kernel_sections_mem();
> >>>>
> >>>> + loongarch_parse_crashkernel();
> >>>> +
> >>>> /*
> >>>> * In order to reduce the possibility of kernel panic when failed to
> >>>> * get IO TLB memory under CONFIG_SWIOTLB, it is better to allocate
> >>>> @@ -290,6 +338,7 @@ static void __init resource_init(void)
> >>>> request_resource(res, &code_resource);
> >>>> request_resource(res, &data_resource);
> >>>> request_resource(res, &bss_resource);
> >>>> + request_crashkernel(res);
> >>>> }
> >>>> }
> >>>>
> >>>> diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c
> >>>> index aa1c95aaf595..0e610872f3f4 100644
> >>>> --- a/arch/loongarch/kernel/traps.c
> >>>> +++ b/arch/loongarch/kernel/traps.c
> >>>> @@ -10,6 +10,7 @@
> >>>> #include <linux/entry-common.h>
> >>>> #include <linux/init.h>
> >>>> #include <linux/kernel.h>
> >>>> +#include <linux/kexec.h>
> >>>> #include <linux/module.h>
> >>>> #include <linux/extable.h>
> >>>> #include <linux/mm.h>
> >>>> @@ -246,6 +247,9 @@ void __noreturn die(const char *str, struct pt_regs *regs)
> >>>>
> >>>> oops_exit();
> >>>>
> >>>> + if (regs && kexec_should_crash(current))
> >>>> + crash_kexec(regs);
> >>>> +
> >>>> if (in_interrupt())
> >>>> panic("Fatal exception in interrupt");
> >>>>
> >>>> --
> >>>> 2.36.0
> >>>>
> >>
>

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