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From: Rob Herring <robh+dt@kernel.org>
To: Nick Kossifidis <mick@ics.forth.gr>, Ard Biesheuvel <ardb@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>,
	linux-riscv <linux-riscv@lists.infradead.org>,
	 Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	 Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	 "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
	<devicetree@vger.kernel.org>
Subject: Re: [PATCH v4 5/5] RISC-V: Add crash kernel support
Date: Wed, 16 Jun 2021 08:55:02 -0600
Message-ID: <CAL_Jsq+9eBSHUwzWBipgoSHNDvxqfrTuY4Un0PrRhoaAHugJNw@mail.gmail.com> (raw)
In-Reply-To: <a488d802940f7fc2ae34a4fe583ec187@mailhost.ics.forth.gr>

+Ard

On Tue, Jun 15, 2021 at 5:29 PM Nick Kossifidis <mick@ics.forth.gr> wrote:
>
> Στις 2021-06-15 22:21, Rob Herring έγραψε:
> > On Tue, Jun 15, 2021 at 12:48 PM Geert Uytterhoeven
> > <geert@linux-m68k.org> wrote:
> >>
> >> Hi Nick,
> >>
> >> On Tue, Jun 15, 2021 at 8:29 PM Nick Kossifidis <mick@ics.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 ?

I believe if we originally booted using UEFI tables, then those are
passed the kdump kernel as well. The original DT may have had a
/memory node, but it's possible it didn't match what was in the UEFI
tables. So using the DT /memory nodes for kdump could give surprising
results. I think reserved regions also come from UEFI. Ard can
probably comment better.

Rob

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Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-19  0:55 [PATCH v4 0/5] RISC-V: Add kexec/kdump support Nick Kossifidis
2021-04-19  0:55 ` [PATCH v4 1/5] RISC-V: Add EM_RISCV to kexec UAPI header Nick Kossifidis
2021-04-19  0:55 ` [PATCH v4 2/5] RISC-V: Add kexec support Nick Kossifidis
2021-04-19  0:55 ` [PATCH v4 3/5] RISC-V: Improve init_resources Nick Kossifidis
2021-04-19  0:55 ` [PATCH v4 4/5] RISC-V: Add kdump support Nick Kossifidis
2021-04-19  0:55 ` [PATCH v4 5/5] RISC-V: Add crash kernel support Nick Kossifidis
2021-06-15 13:19   ` Geert Uytterhoeven
2021-06-15 18:29     ` Nick Kossifidis
2021-06-15 18:48       ` Geert Uytterhoeven
2021-06-15 19:21         ` Rob Herring
2021-06-15 23:29           ` Nick Kossifidis
2021-06-16 14:55             ` Rob Herring [this message]
2021-06-16 16:30               ` Ard Biesheuvel

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