Re: [PATCH V2] mm: Define default value for FIRST_USER_ADDRESS

[Stafford Horne]

On Fri, Apr 16, 2021 at 10:47:34AM +0530, Anshuman Khandual wrote:
> Currently most platforms define FIRST_USER_ADDRESS as 0UL duplication the
> same code all over. Instead just define a generic default value (i.e 0UL)
> for FIRST_USER_ADDRESS and let the platforms override when required. This
> makes it much cleaner with reduced code.
> 
> The default FIRST_USER_ADDRESS here would be skipped in <linux/pgtable.h>
> when the given platform overrides its value via <asm/pgtable.h>.
> 
> Cc: Richard Henderson <rth@xxxxxxxxxxx>
> Cc: Vineet Gupta <vgupta@xxxxxxxxxxxx>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Will Deacon <will@xxxxxxxxxx>
> Cc: Guo Ren <guoren@xxxxxxxxxx>
> Cc: Brian Cain <bcain@xxxxxxxxxxxxxx>
> Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
> Cc: Michal Simek <monstr@xxxxxxxxx>
> Cc: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
> Cc: Ley Foon Tan <ley.foon.tan@xxxxxxxxx>
> Cc: Jonas Bonn <jonas@xxxxxxxxxxxx>
> Cc: Stefan Kristiansson <stefan.kristiansson@xxxxxxxxxxxxx>
> Cc: Stafford Horne <shorne@xxxxxxxxx>
> Cc: "James E.J. Bottomley" <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
> Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx>
> Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx>
> Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
> Cc: Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: Jeff Dike <jdike@xxxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Chris Zankel <chris@xxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: linux-arch@xxxxxxxxxxxxxxx
> Cc: linux-mm@xxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> ---
> This applies on v5.12-rc7 and has been boot tested on arm64 platform.
> But has been cross compiled on multiple other platforms.
> 
> Changes in V2:
> 
> - Dropped ARCH_HAS_FIRST_USER_ADDRESS construct
> 
> Changes in V1:
> 
> https://patchwork.kernel.org/project/linux-mm/patch/1618368899-20311-1-git-send-email-anshuman.khandual@xxxxxxx/
> 
>  arch/alpha/include/asm/pgtable.h             | 1 -
>  arch/arc/include/asm/pgtable.h               | 6 ------
>  arch/arm64/include/asm/pgtable.h             | 2 --
>  arch/csky/include/asm/pgtable.h              | 1 -
>  arch/hexagon/include/asm/pgtable.h           | 3 ---
>  arch/ia64/include/asm/pgtable.h              | 1 -
>  arch/m68k/include/asm/pgtable_mm.h           | 1 -
>  arch/microblaze/include/asm/pgtable.h        | 2 --
>  arch/mips/include/asm/pgtable-32.h           | 1 -
>  arch/mips/include/asm/pgtable-64.h           | 1 -
>  arch/nios2/include/asm/pgtable.h             | 2 --
>  arch/openrisc/include/asm/pgtable.h          | 1 -

Acked-by: Stafford Horne <shorne@xxxxxxxxx>

>  arch/parisc/include/asm/pgtable.h            | 2 --
>  arch/powerpc/include/asm/book3s/pgtable.h    | 1 -
>  arch/powerpc/include/asm/nohash/32/pgtable.h | 1 -
>  arch/powerpc/include/asm/nohash/64/pgtable.h | 2 --
>  arch/riscv/include/asm/pgtable.h             | 2 --
>  arch/s390/include/asm/pgtable.h              | 2 --
>  arch/sh/include/asm/pgtable.h                | 2 --
>  arch/sparc/include/asm/pgtable_32.h          | 1 -
>  arch/sparc/include/asm/pgtable_64.h          | 3 ---
>  arch/um/include/asm/pgtable-2level.h         | 1 -
>  arch/um/include/asm/pgtable-3level.h         | 1 -
>  arch/x86/include/asm/pgtable_types.h         | 2 --
>  arch/xtensa/include/asm/pgtable.h            | 1 -
>  include/linux/pgtable.h                      | 9 +++++++++
>  26 files changed, 9 insertions(+), 43 deletions(-)

This all looks fine to me, will this be merged via the arm tree?  I guess you
have a means for that.

-Stafford