Re: [PATCH v19 05/13] of: Add a common kexec FDT setup function

From: Rob Herring <robh@kernel.org>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>,
	Mimi Zohar <zohar@linux.ibm.com>,
	Thiago Jung Bauermann <bauerman@linux.ibm.com>,
	AKASHI Takahiro <takahiro.akashi@linaro.org>,
	Greg KH <gregkh@linuxfoundation.org>,
	Will Deacon <will@kernel.org>, Joe Perches <joe@perches.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	James Morse <james.morse@arm.com>,
	Sasha Levin <sashal@kernel.org>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Frank Rowand <frowand.list@gmail.com>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	dmitry.kasatkin@gmail.com, James Morris <jmorris@namei.org>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	Pavel Tatashin <pasha.tatashin@soleen.com>,
	Allison Randal <allison@lohutok.net>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Matthias Brugger <mbrugger@suse.com>,
	Hsin-Yi Wang <hsinyi@chromium.org>,
	tao.li@vivo.com, Christophe Leroy <christophe.leroy@c-s.fr>,
	Prakhar Srivastava <prsriva@linux.microsoft.com>,
	balajib@linux.microsoft.com,
	linux-integrity <linux-integrity@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@vger.kernel.org>,
	linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH v19 05/13] of: Add a common kexec FDT setup function
Date: Tue, 15 Jun 2021 08:01:35 -0600	[thread overview]
Message-ID: <CAL_JsqJ2x7zbyP3fAacdfHOWjCVjg6XhraV2YkoBJdZ2jXAMEA@mail.gmail.com> (raw)
In-Reply-To: <CAMuHMdVSuNS4edh-zM0_sbC0i1AAjQ9Y0n_8Mjz=3CALkW4pgg@mail.gmail.com>

On Tue, Jun 15, 2021 at 6:18 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> Hi Lakshmi and Rob,
>
> On Sun, Feb 21, 2021 at 6:52 PM Lakshmi Ramasubramanian
> <nramas@linux.microsoft.com> wrote:
> > From: Rob Herring <robh@kernel.org>
> >
> > Both arm64 and powerpc do essentially the same FDT /chosen setup for
> > kexec.  The differences are either omissions that arm64 should have
> > or additional properties that will be ignored.  The setup code can be
> > combined and shared by both powerpc and arm64.
> >
> > The differences relative to the arm64 version:
> >  - If /chosen doesn't exist, it will be created (should never happen).
> >  - Any old dtb and initrd reserved memory will be released.
> >  - The new initrd and elfcorehdr are marked reserved.
> >  - "linux,booted-from-kexec" is set.
> >
> > The differences relative to the powerpc version:
> >  - "kaslr-seed" and "rng-seed" may be set.
> >  - "linux,elfcorehdr" is set.
> >  - Any existing "linux,usable-memory-range" is removed.
> >
> > Combine the code for setting up the /chosen node in the FDT and updating
> > the memory reservation for kexec, for powerpc and arm64, in
> > of_kexec_alloc_and_setup_fdt() and move it to "drivers/of/kexec.c".
> >
> > Signed-off-by: Rob Herring <robh@kernel.org>
> > Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
>
> > --- /dev/null
> > +++ b/drivers/of/kexec.c
>
> > +/*
> > + * of_kexec_alloc_and_setup_fdt - Alloc and setup a new Flattened Device Tree
> > + *
> > + * @image:             kexec image being loaded.
> > + * @initrd_load_addr:  Address where the next initrd will be loaded.
> > + * @initrd_len:                Size of the next initrd, or 0 if there will be none.
> > + * @cmdline:           Command line for the next kernel, or NULL if there will
> > + *                     be none.
> > + * @extra_fdt_size:    Additional size for the new FDT buffer.
> > + *
> > + * Return: fdt on success, or NULL errno on error.
> > + */
> > +void *of_kexec_alloc_and_setup_fdt(const struct kimage *image,
> > +                                  unsigned long initrd_load_addr,
> > +                                  unsigned long initrd_len,
> > +                                  const char *cmdline, size_t extra_fdt_size)
> > +{
>
> > +       /* Did we boot using an initrd? */
> > +       prop = fdt_getprop(fdt, chosen_node, "linux,initrd-start", NULL);
> > +       if (prop) {
> > +               u64 tmp_start, tmp_end, tmp_size;
> > +
> > +               tmp_start = fdt64_to_cpu(*((const fdt64_t *) prop));
> > +
> > +               prop = fdt_getprop(fdt, chosen_node, "linux,initrd-end", NULL);
> > +               if (!prop) {
> > +                       ret = -EINVAL;
> > +                       goto out;
> > +               }
> > +
> > +               tmp_end = fdt64_to_cpu(*((const fdt64_t *) prop));
>
> Some kernel code assumes "linux,initrd-{start,end}" are 64-bit,
> other code assumes 32-bit.

It can be either. The above code was a merge of arm64 and powerpc both
of which use 64-bit and still only runs on those arches. It looks like
some powerpc platforms may use 32-bit, but this would have been broken
before.

The code in drivers/of/fdt.c handles either case. We should probably
refactor early_init_dt_check_for_initrd() and this function to use a
common routine.

> linux/Documentation/arm/uefi.rst says 64-bit,
> dt-schema/schemas/chosen.yaml says 32-bit.

We should fix that.

Rob