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Date:   Thu, 20 Oct 2022 12:40:24 +0800
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Subject: Re: [PATCH V4 1/2] RISC-V: Add arch_crash_save_vmcoreinfo support
To:     Baoquan He <bhe@redhat.com>
Cc:     paul.walmsley@sifive.com, palmer@dabbelt.com,
        aou@eecs.berkeley.edu, anup@brainfault.org, heiko@sntech.de,
        guoren@kernel.org, mick@ics.forth.gr,
        alexandre.ghiti@canonical.com, vgoyal@redhat.com,
        dyoung@redhat.com, corbet@lwn.net, Conor.Dooley@microchip.com,
        bagasdotme@gmail.com, k-hagio-ab@nec.com, lijiang@redhat.com,
        kexec@lists.infradead.org, linux-doc@vger.kernel.org,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        crash-utility@redhat.com, heinrich.schuchardt@canonical.com,
        hschauhan@nulltrace.org, yixun.lan@gmail.com
References: <20221019103623.7008-1-xianting.tian@linux.alibaba.com>
 <20221019103623.7008-2-xianting.tian@linux.alibaba.com>
 <Y1CtreAKT/SEh4vN@MiWiFi-R3L-srv>
 <30621b3b-47ba-d612-cfb0-583d779691a3@linux.alibaba.com>
 <Y1C681H2mlxX+zqf@MiWiFi-R3L-srv>
From:   Xianting Tian <xianting.tian@linux.alibaba.com>
In-Reply-To: <Y1C681H2mlxX+zqf@MiWiFi-R3L-srv>
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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@linux.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.