# Re: \[PATCH v3 2/8\] \[booke\] Rename mapping based RELOCATABLE to DYNAMIC\_MEMSTART for BookE

- From: Josh Boyer \<hidden\>
- Date: 2011-11-23 16:47:49 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2011/11/9467175
- Thread: https://ratatoskr.run/linuxppc-dev/2011/11/9466995/t.md

```text
On Mon, Nov 14, 2011 at 12:41 AM, Suzuki K. Poulose [ref] wro=
te:
> The current implementation of CONFIG_RELOCATABLE in BookE is based
> on mapping the page aligned kernel load address to KERNELBASE. This
> approach however is not enough for platforms, where the TLB page size
> is large (e.g, 256M on 44x). So we are renaming the RELOCATABLE used
> currently in BookE to DYNAMIC_MEMSTART to reflect the actual method.
>
> The CONFIG_RELOCATABLE for PPC32(BookE) based on processing of the
> dynamic relocations will be introduced in the later in the patch series.
>
> This change would allow the use of the old method of RELOCATABLE for
> platforms which can afford to enforce the page alignment (platforms with
> smaller TLB size).

I'm OK with the general direction, but this touches a lot of non-4xx
code.  I'd prefer it if Ben took this directly on whatever final
solution is done.

> I haven tested this change only on 440x. I don't have an FSL BookE to ver=
ify
> the changes there.
>
> Scott,
> Could you please test this patch on FSL and let me know the results ?

Scott, did you ever get around to testing this?  In my opinion, this
shouldn't go in without a Tested-by: from someone that tried it on an
FSL platform.

> Suggested-by: Scott Wood <redacted>
>
> Signed-off-by: Suzuki K. Poulose <redacted>
> Cc: =A0 =A0 Scott Wood <redacted>
> Cc: =A0 =A0 Kumar Gala <redacted>
> Cc: =A0 =A0 Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: =A0 =A0 linux ppc dev <redacted>
> ---
>
> =A0arch/powerpc/Kconfig =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0| =A0 50 ++++++++++++++++---------
> =A0arch/powerpc/configs/44x/iss476-smp_defconfig | =A0 =A02 +
> =A0arch/powerpc/include/asm/kdump.h =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A05=
 ++-
> =A0arch/powerpc/include/asm/page.h =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A04=
 +-
> =A0arch/powerpc/kernel/crash_dump.c =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A04=
 +-
> =A0arch/powerpc/kernel/head_44x.S =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =
=A04 ++
> =A0arch/powerpc/kernel/head_fsl_booke.S =A0 =A0 =A0 =A0 =A0| =A0 =A02 +
> =A0arch/powerpc/kernel/machine_kexec.c =A0 =A0 =A0 =A0 =A0 | =A0 =A02 +
> =A0arch/powerpc/kernel/prom_init.c =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A02=
 +
> =A0arch/powerpc/mm/44x_mmu.c =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =
=A0 =A02 +
> =A010 files changed, 47 insertions(+), 30 deletions(-)
>
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index d7c2d1a..8d4f789 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -363,7 +363,8 @@ config KEXEC
> =A0config CRASH_DUMP
> =A0 =A0 =A0 =A0bool "Build a kdump crash kernel"
> =A0 =A0 =A0 =A0depends on PPC64 || 6xx || FSL_BOOKE
> - =A0 =A0 =A0 select RELOCATABLE if PPC64 || FSL_BOOKE
> + =A0 =A0 =A0 select RELOCATABLE if PPC64
> + =A0 =A0 =A0 select DYNAMIC_MEMSTART if FSL_BOOKE
> =A0 =A0 =A0 =A0help
> =A0 =A0 =A0 =A0 =A0Build a kernel suitable for use as a kdump capture ker=
nel.
> =A0 =A0 =A0 =A0 =A0The same kernel binary can be used as production kerne=
l and dump
> @@ -841,23 +842,36 @@ config LOWMEM_CAM_NUM
> =A0 =A0 =A0 =A0int "Number of CAMs to use to map low memory" if LOWMEM_CA=
M_NUM_BOOL
> =A0 =A0 =A0 =A0default 3
>
> -config RELOCATABLE
> - =A0 =A0 =A0 bool "Build a relocatable kernel (EXPERIMENTAL)"
> +config DYNAMIC_MEMSTART

OK, so my one bikeshed comment here.

We add DYNAMIC_MEMSTART for 32-bit, and we have RELOCATABLE for
64-bit.  Then throughout almost the rest of the patch, all we're doing
is duplicating what RELOCATABLE already did (e.g. if ! either thing).
It works, but it is kind of ugly.

Instead, could we define a helper config variable that can be used in
place of that construct?  Something like:

config NONSTATIC_KERNEL (or whatever)
    bool
    default n

...

config DYNAMIC_MEMSTART
    <blah>
    select NONSTATIC_KERNEL

...

config RELOCATABLE
    <blah>
    select NONSTATIC_KERNEL


Then you can do this kind of thing:

       default "0x02000000" if PPC_STD_MMU && CRASH_DUMP && !(NONSTATIC_KER=
NEL)

#if defined(CONFIG_CRASH_DUMP) && !(defined(CONFIG_NONSTATIC_KERNEL))

instead of this:

       default "0x02000000" if PPC_STD_MMU && CRASH_DUMP &&
!(RELOCATABLE || DYNAMIC_MEMSTART)
#if defined(CONFIG_CRASH_DUMP) && !(defined(CONFIG_RELOCATABLE) || \
                                   defined(CONFIG_DYNAMIC_MEMSTART))

while still allowing for differences between RELOCATABLE and DYNAMIC_MEMSTA=
RT.

Thoughts?

josh
```