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Message-ID: <3c8beab1-3ca7-c3d7-6f31-c28a0ae008a3@linux.alibaba.com>
Date:   Wed, 26 Oct 2022 17:44:52 +0800
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Subject: Re: [PATCH V4 1/2] RISC-V: Add arch_crash_save_vmcoreinfo support
To:     Conor Dooley <conor.dooley@microchip.com>
Cc:     Baoquan He <bhe@redhat.com>, Palmer Dabbelt <palmer@dabbelt.com>,
        paul.walmsley@sifive.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,
        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>
 <6af05838-fa58-8197-f3ce-ca95457077a7@linux.alibaba.com>
 <5df30e57-88ae-0a3b-2c1a-b962363d8670@linux.alibaba.com>
 <Y1j9AAhJXpoCx48N@wendy>
From:   Xianting Tian <xianting.tian@linux.alibaba.com>
In-Reply-To: <Y1j9AAhJXpoCx48N@wendy>
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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.

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@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.
>>>