linux-kernel - Re: linux-next: manual merge of the devicetree tree with the powerpc tree

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Message-ID: <CAL_JsqJ9Ske4hkWn3uo8-nef29MQ1DkNdtE=gxbqj8CKrtQorg@mail.gmail.com>
Date:   Thu, 18 Feb 2021 07:52:52 -0600
From:   Rob Herring <robherring2@...il.com>
To:     Stephen Rothwell <sfr@...b.auug.org.au>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        PowerPC <linuxppc-dev@...ts.ozlabs.org>,
        Hari Bathini <hbathini@...ux.ibm.com>,
        Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: linux-next: manual merge of the devicetree tree with the powerpc tree

On Thu, Feb 18, 2021 at 5:34 AM Stephen Rothwell <sfr@...b.auug.org.au> wrote:
>
> Hi Michael,
>
> On Thu, 18 Feb 2021 21:44:37 +1100 Michael Ellerman <mpe@...erman.id.au> wrote:
> >
> > I think it just needs this?
> >
> > diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c
> > index 87e34611f93d..0492ca6003f3 100644
> > --- a/arch/powerpc/kexec/elf_64.c
> > +++ b/arch/powerpc/kexec/elf_64.c
> > @@ -104,7 +104,7 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
> >
> >       fdt = of_kexec_alloc_and_setup_fdt(image, initrd_load_addr,
> >                                          initrd_len, cmdline,
> > -                                        fdt_totalsize(initial_boot_params));
> > +                                        kexec_fdt_totalsize_ppc64(image));
> >       if (!fdt) {
> >               pr_err("Error setting up the new device tree.\n");
> >               ret = -EINVAL;
> >
>
> I thought about that, but the last argument to
> of_kexec_alloc_and_setup_fdt() is extra_fdt_size and the allocation
> done is for this:
>
> fdt_size = fdt_totalsize(initial_boot_params) +
>                    (cmdline ? strlen(cmdline) : 0) +
>                    FDT_EXTRA_SPACE +
>                    extra_fdt_size;
>
> and kexec_fdt_totalsize_ppc64() also includes
> fdt_totalsize(initial_boot_params) so I was not sure.  Maybe
> kexec_fdt_totalsize_ppc64() needs modification as well?

You're both right. Michael's fix is sufficient for the merge. The only
risk with a larger size is failing to allocate it, but we're talking
only 10s of KB. Historically until the commit causing the conflict,
PPC was just used 2x fdt_totalsize(initial_boot_params). You could
drop 'fdt_size = fdt_totalsize(initial_boot_params) + (2 *
COMMAND_LINE_SIZE);' from kexec_fdt_totalsize_ppc64() as well, but
then the function name is misleading.

Lakshmi can send a follow-up patch to fine tune the size and rename
kexec_fdt_totalsize_ppc64.

Rob