linux-kernel - Re: [PATCH v4 5/5] RISC-V: Add crash kernel support

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Message-ID: <a488d802940f7fc2ae34a4fe583ec187@mailhost.ics.forth.gr>
Date:   Wed, 16 Jun 2021 02:29:19 +0300
From:   Nick Kossifidis <mick@....forth.gr>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Nick Kossifidis <mick@....forth.gr>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH v4 5/5] RISC-V: Add crash kernel support

Στις 2021-06-15 22:21, Rob Herring έγραψε:
> On Tue, Jun 15, 2021 at 12:48 PM Geert Uytterhoeven
> <geert@...ux-m68k.org> wrote:
>> 
>> Hi Nick,
>> 
>> On Tue, Jun 15, 2021 at 8:29 PM Nick Kossifidis <mick@....forth.gr> 
>> wrote:
>> > Στις 2021-06-15 16:19, Geert Uytterhoeven έγραψε:
>> > > This does not match
>> > > https://github.com/devicetree-org/dt-schema/blob/master/schemas/chosen.yaml#L77:
>> > >
>> > >     $ref: types.yaml#/definitions/uint64-array
>> > >     maxItems: 2
>> > >     description:
>> > >       This property (currently used only on arm64) holds the memory
>> > > range,
>> > >       the address and the size, of the elf core header which mainly
>> > > describes
>> > >       the panicked kernel\'s memory layout as PT_LOAD segments of elf
>> > > format.
>> > >
>> > > Hence "linux,elfcorehdr" should be a property of the /chosen node,
>> > > instead of a memory node with a compatible value of "linux,elfcorehdr".
>> > >
>> >
>> > That's a binding for a property on the /chosen node, that as the text
>> > says it's defined for arm64 only and the code that handled it was also
>> 
>> That doesn't mean it must not be used on other architectures ;-)
>> Arm64 was just the first one to use it...
> 
> It is used on arm64 because memory is often passed by UEFI tables and
> not with /memory node. As riscv is also supporting EFI, I'd think they
> would do the same.
> 

We've had this discussion before, riscv uses /memory for now and even if 
we switched to getting memory from ACPI/UEFI tables, the elf core header 
is passed from the crashed kernel to the kdump kernel, it has nothing to 
do with UEFI since the bootloader is the kernel itself. Am I missing 
something ?

Regards,
Nick