Re: [PATCH v4 02/10] memblock: Add variables for usable memory limitation

From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Rob Herring <robh@kernel.org>
Cc: Russell King <linux@armlinux.org.uk>,
	Nicolas Pitre <nico@fluxnic.net>,
	 Ard Biesheuvel <ardb@kernel.org>,
	Linus Walleij <linus.walleij@linaro.org>,
	 Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	 Nick Kossifidis <mick@ics.forth.gr>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	 Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	 Frank Rowand <frowand.list@gmail.com>,
	Dave Young <dyoung@redhat.com>,  Mike Rapoport <rppt@kernel.org>,
	Baoquan He <bhe@redhat.com>, Vivek Goyal <vgoyal@redhat.com>,
	 Andrew Morton <akpm@linux-foundation.org>,
	 "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
	<devicetree@vger.kernel.org>,
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	 linux-riscv <linux-riscv@lists.infradead.org>,
	kexec@lists.infradead.org,  Linux MM <linux-mm@kvack.org>,
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	 Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4 02/10] memblock: Add variables for usable memory limitation
Date: Wed, 11 Aug 2021 10:11:34 +0200	[thread overview]
Message-ID: <CAMuHMdVRPpHudj2svs_TYP9=GYkWFtJrG_+BHA7A+TVPdQ92aQ@mail.gmail.com> (raw)
In-Reply-To: <20210714135101.GB2441138@robh.at.kernel.org>

On Wed, Jul 14, 2021 at 3:51 PM Rob Herring <robh@kernel.org> wrote:
> On Wed, Jul 14, 2021 at 02:50:12PM +0200, Geert Uytterhoeven wrote:
> > Add two global variables (cap_mem_addr and cap_mem_size) for storing a
> > base address and size, describing a limited region in which memory may
> > be considered available for use by the kernel.  If enabled, memory
> > outside of this range is not available for use.
> >
> > These variables can by filled by firmware-specific code, and used in
> > calls to memblock_cap_memory_range() by architecture-specific code.
> > An example user is the parser of the "linux,usable-memory-range"
> > property in the DT "/chosen" node.
> >
> > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> > ---
> > This is similar to how the initial ramdisk (phys_initrd_{start,size})
> > and ELF core headers (elfcorehdr_{addr,size})) are handled.
> >
> > Does there exist a suitable place in the common memblock code to call
> > "memblock_cap_memory_range(cap_mem_addr, cap_mem_size)", or does this
> > have to be done in architecture-specific code?
>
> Can't you just call it from early_init_dt_scan_usablemem? If the
> property is present, you want to call it. If the property is not
> present, nothing happens.

Seems to work fine when called from early_init_dt_scan_nodes().
Hence v5 will no longer need to touch memblock.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

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