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Message-ID: <e76bcf5d-08c9-1d2f-8c04-149b17236929@loongson.cn>
Date: Mon, 5 Sep 2022 10:04:22 +0800
From: Youling Tang <tangyouling@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>
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>,
kexec@...ts.infradead.org, loongarch@...ts.linux.dev,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] LoongArch: Add kdump support
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@...ngson.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?
Youling.
>
> Huacai
>>
>>>
>>> Huacai
>>>
>>> On Mon, Aug 29, 2022 at 12:37 PM Youling Tang <tangyouling@...ngson.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@...0M"), 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@...ngson.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@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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