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Date:   Thu, 20 Oct 2022 11:05:23 +0800
From:   Baoquan He <bhe@redhat.com>
To:     Xianting Tian <xianting.tian@linux.alibaba.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
Subject: Re: [PATCH V4 1/2] RISC-V: Add arch_crash_save_vmcoreinfo support
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References: <20221019103623.7008-1-xianting.tian@linux.alibaba.com>
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 <30621b3b-47ba-d612-cfb0-583d779691a3@linux.alibaba.com>
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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()?