From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christophe Leroy Date: Wed, 14 Apr 2021 06:10:49 +0000 Subject: Re: [PATCH] mm: Define ARCH_HAS_FIRST_USER_ADDRESS Message-Id: List-Id: References: <1618368899-20311-1-git-send-email-anshuman.khandual@arm.com> <6d24d3cc-b2df-f0d7-f4bf-f505f679c77e@arm.com> In-Reply-To: <6d24d3cc-b2df-f0d7-f4bf-f505f679c77e@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit To: Anshuman Khandual , linux-mm@kvack.org, akpm@linux-foundation.org Cc: linux-s390@vger.kernel.org, x86@kernel.org, linux-ia64@vger.kernel.org, linux-parisc@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-xtensa@linux-xtensa.org, linux-sh@vger.kernel.org, linux-um@lists.infradead.org, linux-mips@vger.kernel.org, linux-csky@vger.kernel.org, linux-kernel@vger.kernel.org, linux-m68k@lists.linux-m68k.org, openrisc@lists.librecores.org, linux-alpha@vger.kernel.org, sparclinux@vger.kernel.org, linux-riscv@lists.infradead.org, linux-snps-arc@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org 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@vger.kernel.org >>> Cc: linux-snps-arc@lists.infradead.org >>> Cc: linux-arm-kernel@lists.infradead.org >>> Cc: linux-csky@vger.kernel.org >>> Cc: linux-hexagon@vger.kernel.org >>> Cc: linux-ia64@vger.kernel.org >>> Cc: linux-m68k@lists.linux-m68k.org >>> Cc: linux-mips@vger.kernel.org >>> Cc: openrisc@lists.librecores.org >>> Cc: linux-parisc@vger.kernel.org >>> Cc: linuxppc-dev@lists.ozlabs.org >>> Cc: linux-riscv@lists.infradead.org >>> Cc: linux-s390@vger.kernel.org >>> Cc: linux-sh@vger.kernel.org >>> Cc: sparclinux@vger.kernel.org >>> Cc: linux-um@lists.infradead.org >>> Cc: linux-xtensa@linux-xtensa.org >>> Cc: x86@kernel.org >>> Cc: linux-mm@kvack.org >>> Cc: linux-kernel@vger.kernel.org >>> Signed-off-by: Anshuman Khandual >>> --- >>>   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.