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Date:   Wed, 26 Oct 2022 10:25:20 +0100
From:   Conor Dooley <conor.dooley@microchip.com>
To:     Xianting Tian <xianting.tian@linux.alibaba.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>
Subject: Re: [PATCH V4 1/2] RISC-V: Add arch_crash_save_vmcoreinfo support
Message-ID: <Y1j9AAhJXpoCx48N@wendy>
References: <20221019103623.7008-1-xianting.tian@linux.alibaba.com>
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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.

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.
> >