Re: [PATCH] mm: Define ARCH_HAS_FIRST_USER_ADDRESS
From: Christophe Leroy
Date: Wed Apr 14 2021 - 02:11:01 EST
Le 14/04/2021 à 07:59, Anshuman Khandual a écrit :
On 4/14/21 10:52 AM, Christophe Leroy wrote:
Le 14/04/2021 à 04:54, Anshuman Khandual a écrit :
Currently most platforms define FIRST_USER_ADDRESS as 0UL duplicating the
same code all over. Instead define a new option ARCH_HAS_FIRST_USER_ADDRESS
for those platforms which would override generic default FIRST_USER_ADDRESS
value 0UL. This makes it much cleaner with reduced code.
Cc: linux-alpha@xxxxxxxxxxxxxxx
Cc: linux-snps-arc@xxxxxxxxxxxxxxxxxxx
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: linux-csky@xxxxxxxxxxxxxxx
Cc: linux-hexagon@xxxxxxxxxxxxxxx
Cc: linux-ia64@xxxxxxxxxxxxxxx
Cc: linux-m68k@xxxxxxxxxxxxxxxxxxxx
Cc: linux-mips@xxxxxxxxxxxxxxx
Cc: openrisc@xxxxxxxxxxxxxxxxxxxx
Cc: linux-parisc@xxxxxxxxxxxxxxx
Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
Cc: linux-riscv@xxxxxxxxxxxxxxxxxxx
Cc: linux-s390@xxxxxxxxxxxxxxx
Cc: linux-sh@xxxxxxxxxxxxxxx
Cc: sparclinux@xxxxxxxxxxxxxxx
Cc: linux-um@xxxxxxxxxxxxxxxxxxx
Cc: linux-xtensa@xxxxxxxxxxxxxxxx
Cc: x86@xxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
---
arch/alpha/include/asm/pgtable.h | 1 -
arch/arc/include/asm/pgtable.h | 6 ------
arch/arm/Kconfig | 1 +
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/nds32/Kconfig | 1 +
arch/nios2/include/asm/pgtable.h | 2 --
arch/openrisc/include/asm/pgtable.h | 1 -
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/mm.h | 4 ++++
mm/Kconfig | 4 ++++
29 files changed, 10 insertions(+), 43 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 8ba434287387..47098ccd715e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -46,6 +46,10 @@ extern int sysctl_page_lock_unfairness;
void init_mm_internals(void);
+#ifndef ARCH_HAS_FIRST_USER_ADDRESS
I guess you didn't test it ..... :)
In fact I did :) Though just booted it on arm64 and cross compiled on
multiple others platforms.
should be #ifndef CONFIG_ARCH_HAS_FIRST_USER_ADDRESS
Right, meant that instead.
+#define FIRST_USER_ADDRESS 0UL
+#endif
But why do we need a config option at all for that ?
Why not just:
#ifndef FIRST_USER_ADDRESS
#define FIRST_USER_ADDRESS 0UL
#endif
This sounds simpler. But just wondering, would not there be any possibility
of build problems due to compilation sequence between arch and generic code ?
For sure it has to be addresses carefully, but there are already a lot of stuff like that around
pgtables.h
For instance, pte_offset_kernel() has a generic definition in linux/pgtables.h based on whether it
is already defined or not.
Taking into account that FIRST_USER_ADDRESS is today in the architectures's asm/pgtables.h, I think
putting the fallback definition in linux/pgtable.h would do the trick.