[PATCH 2/3] LoongArch: Add kdump support

Huacai Chen chenhuacai at kernel.org
Sun Sep 4 19:14:15 PDT 2022


On Mon, Sep 5, 2022 at 10:04 AM Youling Tang <tangyouling at loongson.cn> 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 at loongson.cn> 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 at loongson.cn> 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 at 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 at loongson.cn>
> >>>> ---
> >>>>  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 at 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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