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

[Huacai Chen]

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.

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
> >>
>