linux-kernel - Re: [PATCH V4 1/2] RISC-V: Add arch_crash_save

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Date:   Wed, 26 Oct 2022 22:22:53 +0800
From:   Xianting Tian <xianting.tian@...ux.alibaba.com>
To:     Baoquan He <bhe@...hat.com>
Cc:     Conor Dooley <conor.dooley@...rochip.com>,
        Palmer Dabbelt <palmer@...belt.com>, paul.walmsley@...ive.com,
        aou@...s.berkeley.edu, anup@...infault.org, heiko@...ech.de,
        guoren@...nel.org, mick@....forth.gr,
        alexandre.ghiti@...onical.com, vgoyal@...hat.com,
        dyoung@...hat.com, corbet@....net, bagasdotme@...il.com,
        k-hagio-ab@....com, lijiang@...hat.com, kexec@...ts.infradead.org,
        linux-doc@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org, crash-utility@...hat.com,
        heinrich.schuchardt@...onical.com, hschauhan@...ltrace.org,
        yixun.lan@...il.com
Subject: Re: [PATCH V4 1/2] RISC-V: Add arch_crash_save_vmcoreinfo support


在 2022/10/26 下午8:05, Baoquan He 写道:
> Hi Xianting,
>
> On 10/26/22 at 05:44pm, Xianting Tian wrote:
>> 在 2022/10/26 下午5:25, Conor Dooley 写道:
>>> On Wed, Oct 26, 2022 at 05:08:11PM +0800, Xianting Tian wrote:
>>>> Hi Palmer, Conor
>>>>
>>>> Is this version OK for you?
>>> The weird ifdef/IS_ENABLED thing was the only comment I had. It's a bit
>>> odd & I notice Baoquan brought it up too. I didn't (and won't) give you
>>> a reviewed by on these patches because I don't understand the area well
>>> enough. The general nitpickery seems to be sorted though.
>> I checked the KERNEL_LINK_ADDR definition of riscv,  it is valid for
>> CONFIG_64BIT and !CONFIG_64BIT.
> This series looks good to me. My only minor concern is if we can make
> the arch_crash_save_vmcoreinfo() as below. I don't understand why we
> have to have the CONFIG_64BIT ifdeffery and the IS_ENABLED(CONFIG_64BIT)
> between two adjacent code blocks. Not sure if we are saying the same
> thing.

KERNEL_LINK_ADDR is valid for both CONFIG_64BIT and !CONFIG_64BIT, but  
MODULES_VADDR is only defined when CONFIG_64BIT.

I tend to agree only remove IS_ENABLED, thanks

For riscv:

#ifdef CONFIG_64BIT

/* Leave 2GB for kernel and BPF at the end of the address space */
#define KERNEL_LINK_ADDR        (ADDRESS_SPACE_END - SZ_2G + 1)
#else
#define KERNEL_LINK_ADDR        PAGE_OFFSET
#endif
>
> +void arch_crash_save_vmcoreinfo(void)
> +{
> +       VMCOREINFO_NUMBER(VA_BITS);
> +       VMCOREINFO_NUMBER(phys_ram_base);
> +
> +       vmcoreinfo_append_str("NUMBER(PAGE_OFFSET)=0x%lx\n", PAGE_OFFSET);
> +       vmcoreinfo_append_str("NUMBER(VMALLOC_START)=0x%lx\n", VMALLOC_START);
> +       vmcoreinfo_append_str("NUMBER(VMALLOC_END)=0x%lx\n", VMALLOC_END);
> +       vmcoreinfo_append_str("NUMBER(VMEMMAP_START)=0x%lx\n", VMEMMAP_START);
> +       vmcoreinfo_append_str("NUMBER(VMEMMAP_END)=0x%lx\n", VMEMMAP_END);
> +#ifdef CONFIG_64BIT
> +	vmcoreinfo_append_str("NUMBER(MODULES_VADDR)=0x%lx\n", MODULES_VADDR);
> +       vmcoreinfo_append_str("NUMBER(MODULES_END)=0x%lx\n", MODULES_END);
> +       vmcoreinfo_append_str("NUMBER(KERNEL_LINK_ADDR)=0x%lx\n", KERNEL_LINK_ADDR);
> +#endif
> +}
>
>> Maybe we can remove IS_ENABLED(CONFIG_64BIT)
>>
>> arch/riscv/include/asm/pgtable.h
>> #define ADDRESS_SPACE_END       (UL(-1))
>> #ifdef CONFIG_64BIT
>> /* Leave 2GB for kernel and BPF at the end of the address space */
>> #define KERNEL_LINK_ADDR        (ADDRESS_SPACE_END - SZ_2G + 1)
>> #else
>> #define KERNEL_LINK_ADDR        PAGE_OFFSET
>> #endif
>>
>> arch/riscv/include/asm/page.h
>> #ifdef CONFIG_64BIT
>> #ifdef CONFIG_MMU
>> #define PAGE_OFFSET             kernel_map.page_offset
>> #else
>> #define PAGE_OFFSET             _AC(CONFIG_PAGE_OFFSET, UL)
>> #endif
>> /*
>>   * By default, CONFIG_PAGE_OFFSET value corresponds to SV48 address space so
>>   * define the PAGE_OFFSET value for SV39.
>>   */
>> #define PAGE_OFFSET_L4          _AC(0xffffaf8000000000, UL)
>> #define PAGE_OFFSET_L3          _AC(0xffffffd800000000, UL)
>> #else
>> #define PAGE_OFFSET             _AC(CONFIG_PAGE_OFFSET, UL)
>> #endif /* CONFIG_64BIT */
>>
>>> Thanks,
>>> Conor.
>>>
>>>> 在 2022/10/20 下午12:40, Xianting Tian 写道:
>>>>> 在 2022/10/20 上午11:05, Baoquan He 写道:
>>>>>> On 10/20/22 at 10:17am, Xianting Tian wrote:
>>>>>>> 在 2022/10/20 上午10:08, Baoquan He 写道:
>>>>>>>> On 10/19/22 at 06:36pm, Xianting Tian wrote:
>>>>>>>>> Add arch_crash_save_vmcoreinfo(), which exports VM
>>>>>>>>> layout(MODULES, VMALLOC,
>>>>>>>>> VMEMMAP ranges and KERNEL_LINK_ADDR), va bits and ram
>>>>>>>>> base for vmcore.
>>>>>>>>>
>>>>>>>>> Default pagetable levels and PAGE_OFFSET aren't same for
>>>>>>>>> different kernel
>>>>>>>>> version as below. For pagetable levels, it sets sv57 by
>>>>>>>>> default and falls
>>>>>>>>> back to setting sv48 at boot time if sv57 is not
>>>>>>>>> supported by the hardware.
>>>>>>>>>
>>>>>>>>> For ram base, the default value is 0x80200000 for qemu
>>>>>>>>> riscv64 env and,
>>>>>>>>> for example, is 0x200000 on the XuanTie 910 CPU.
>>>>>>>>>
>>>>>>>>>      * Linux Kernel 5.18 ~
>>>>>>>>>      *      PGTABLE_LEVELS = 5
>>>>>>>>>      *      PAGE_OFFSET = 0xff60000000000000
>>>>>>>>>      * Linux Kernel 5.17 ~
>>>>>>>>>      *      PGTABLE_LEVELS = 4
>>>>>>>>>      *      PAGE_OFFSET = 0xffffaf8000000000
>>>>>>>>>      * Linux Kernel 4.19 ~
>>>>>>>>>      *      PGTABLE_LEVELS = 3
>>>>>>>>>      *      PAGE_OFFSET = 0xffffffe000000000
>>>>>>>>>
>>>>>>>>> Since these configurations change from time to time and
>>>>>>>>> version to version,
>>>>>>>>> it is preferable to export them via vmcoreinfo than to
>>>>>>>>> change the crash's
>>>>>>>>> code frequently, it can simplify the development of crash tool.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Xianting Tian <xianting.tian@...ux.alibaba.com>
>>>>>>>>> ---
>>>>>>>>>      arch/riscv/kernel/Makefile     |  1 +
>>>>>>>>>      arch/riscv/kernel/crash_core.c | 23 +++++++++++++++++++++++
>>>>>>>>>      2 files changed, 24 insertions(+)
>>>>>>>>>      create mode 100644 arch/riscv/kernel/crash_core.c
>>>>>>>>>
>>>>>>>>> diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
>>>>>>>>> index db6e4b1294ba..4cf303a779ab 100644
>>>>>>>>> --- a/arch/riscv/kernel/Makefile
>>>>>>>>> +++ b/arch/riscv/kernel/Makefile
>>>>>>>>> @@ -81,6 +81,7 @@ obj-$(CONFIG_KGDB)        += kgdb.o
>>>>>>>>>      obj-$(CONFIG_KEXEC_CORE)    += kexec_relocate.o
>>>>>>>>> crash_save_regs.o machine_kexec.o
>>>>>>>>>      obj-$(CONFIG_KEXEC_FILE)    += elf_kexec.o machine_kexec_file.o
>>>>>>>>>      obj-$(CONFIG_CRASH_DUMP)    += crash_dump.o
>>>>>>>>> +obj-$(CONFIG_CRASH_CORE)    += crash_core.o
>>>>>>>>>      obj-$(CONFIG_JUMP_LABEL)    += jump_label.o
>>>>>>>>> diff --git a/arch/riscv/kernel/crash_core.c
>>>>>>>>> b/arch/riscv/kernel/crash_core.c
>>>>>>>>> new file mode 100644
>>>>>>>>> index 000000000000..3e889d0ed7bd
>>>>>>>>> --- /dev/null
>>>>>>>>> +++ b/arch/riscv/kernel/crash_core.c
>>>>>>>>> @@ -0,0 +1,23 @@
>>>>>>>>> +// SPDX-License-Identifier: GPL-2.0-only
>>>>>>>>> +
>>>>>>>>> +#include <linux/crash_core.h>
>>>>>>>>> +#include <linux/pagemap.h>
>>>>>>>>> +
>>>>>>>>> +void arch_crash_save_vmcoreinfo(void)
>>>>>>>>> +{
>>>>>>>>> +    VMCOREINFO_NUMBER(VA_BITS);
>>>>>>>>> +    VMCOREINFO_NUMBER(phys_ram_base);
>>>>>>>>> +
>>>>>>>>> +
>>>>>>>>> vmcoreinfo_append_str("NUMBER(PAGE_OFFSET)=0x%lx\n",
>>>>>>>>> PAGE_OFFSET);
>>>>>>>>> + vmcoreinfo_append_str("NUMBER(VMALLOC_START)=0x%lx\n",
>>>>>>>>> VMALLOC_START);
>>>>>>>>> +
>>>>>>>>> vmcoreinfo_append_str("NUMBER(VMALLOC_END)=0x%lx\n",
>>>>>>>>> VMALLOC_END);
>>>>>>>>> + vmcoreinfo_append_str("NUMBER(VMEMMAP_START)=0x%lx\n",
>>>>>>>>> VMEMMAP_START);
>>>>>>>>> +
>>>>>>>>> vmcoreinfo_append_str("NUMBER(VMEMMAP_END)=0x%lx\n",
>>>>>>>>> VMEMMAP_END);
>>>>>>>>> +#ifdef CONFIG_64BIT
>>>>>>>>> + vmcoreinfo_append_str("NUMBER(MODULES_VADDR)=0x%lx\n",
>>>>>>>>> MODULES_VADDR);
>>>>>>>>> +
>>>>>>>>> vmcoreinfo_append_str("NUMBER(MODULES_END)=0x%lx\n",
>>>>>>>>> MODULES_END);
>>>>>>>>> +#endif
>>>>>>>>> +
>>>>>>>>> +    if (IS_ENABLED(CONFIG_64BIT))
>>>>>>>>> +
>>>>>>>>> vmcoreinfo_append_str("NUMBER(KERNEL_LINK_ADDR)=0x%lx\n",
>>>>>>>>> KERNEL_LINK_ADDR);
>>>>>>>> Wondering why you don't put KERNEL_LINK_ADDR exporting into the above
>>>>>>>> ifdeffery scope, with that you can save one line of
>>>>>>>> "IS_ENABLED(CONFIG_64BIT)".
>>>>>>> I followed the rule in print_vm_layout() of
>>>>>>> arch/riscv/mm/init.c, which used
>>>>>>> IS_ENABLED when print the value of KERNEL_LINK_ADDR.
>>>>>>>
>>>>>> I see. There's PAGE_OFFSET in the middle. Thanks.
>>>>>>
>>>>>>            print_ml("lowmem", (unsigned long)PAGE_OFFSET,
>>>>>>                    (unsigned long)high_memory)
>>>>>>
>>>>>> So now, do you think if it's necessary to have another
>>>>>> IS_ENABLED(CONFIG_64BIT) in the current arch_crash_save_vmcoreinfo()?
>>>>> For which MACRO?  I think current code for PAGE_OFFSET is OK.
>>>>>