Messages in this thread | | | Date | Fri, 02 Jul 2021 18:56:55 +0300 | From | Nick Kossifidis <> | Subject | Re: [PATCH 2/3] riscv: Remove non-standard linux,elfcorehdr handling |
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Στις 2021-07-01 05:52, Palmer Dabbelt έγραψε: > On Wed, 16 Jun 2021 07:47:46 PDT (-0700), robh+dt@kernel.org wrote: >> On Wed, Jun 16, 2021 at 4:43 AM Nick Kossifidis <mick@ics.forth.gr> >> wrote: >>> >>> Στις 2021-06-16 10:56, Geert Uytterhoeven έγραψε: >>> > >>> > I can't comment on the duplication on arm64, but to me, /chosen >>> > sounds like the natural place for both "linux,elfcorehdr" and >>> > "linux,usable-memory-range". First rule of DT is "DT describes >>> > hardware, not software policy", with /chosen describing some software >>> > configuration. >>> > >>> >>> We already have "linux,usable-memory" on /memory node: >>> https://elixir.bootlin.com/linux/v5.13-rc6/source/drivers/of/fdt.c#L1011 >>> and it makes perfect sense to be there since it overrides /memory's >>> reg >>> property. >>> >>> Why define another binding for the same thing on /chosen ? >> >> Go look at the thread adding "linux,usable-memory-range". There were >> only 35 versions of it[1]. I wasn't happy with a 2nd way either, but >> as I've mentioned before we don't always have /memory node. > > I don't really understand what's going on here, but IIUC what I merged > in 5.13 doesn't match the behavior that other architectures have. In > that case I'm happy moving RISC-V over to the more standard way of > doing things and just calling what we have in 5.13 a screwup. > > Sorry for the confusion.
Long story short:
a) We use "linux,usable-memory" on /memory node to limit the memory of the kdump kernel, it's a standard binding defined at: https://elixir.bootlin.com/linux/v5.13-rc6/source/drivers/of/fdt.c#L1011
b) We used a reserved region (again a standard binding) named "linux,elfcorehdr" which has the same name as a property on /chosen used by arm64 for the same thing. With this patch we 'll use arm64's approach, although it's a bit worse since we'll need to add the same region twice on the fdt (once in /chosen as a property and another one in the reservation map so that it gets reserved during early boot).
Fortunately I (still) haven't posted the kexec-tools patches on the mailing list so we don't break userspace by doing this.
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