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Date: Mon, 5 Sep 2022 10:21:53 +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
On 09/05/2022 10:14 AM, Huacai Chen wrote:
> On Mon, Sep 5, 2022 at 10:04 AM Youling Tang <tangyouling@...ngson.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@...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?
> I don't want to touch smp.c, all merged into machine_kexec.c seems reasonable.
Ok, I'll merge all into machine_kexec.c.
Youling.
>
> Huacai
>>
>> 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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