From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 44CF3CCA484 for ; Sun, 5 Jun 2022 09:58:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244931AbiFEJ6U (ORCPT ); Sun, 5 Jun 2022 05:58:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38992 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229493AbiFEJ6T (ORCPT ); Sun, 5 Jun 2022 05:58:19 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 0A0242BD0; Sun, 5 Jun 2022 02:58:18 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B9300D6E; Sun, 5 Jun 2022 02:58:17 -0700 (PDT) Received: from [10.163.37.253] (unknown [10.163.37.253]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2FB513F66F; Sun, 5 Jun 2022 02:58:08 -0700 (PDT) Message-ID: <53c7da54-e106-0161-a128-4f0cfe92d7e4@arm.com> Date: Sun, 5 Jun 2022 15:28:08 +0530 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Subject: Re: [PATCH 2/6] s390/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT Content-Language: en-US To: Christophe Leroy , "linux-mm@kvack.org" Cc: Catalin Marinas , "linux-kernel@vger.kernel.org" , Paul Mackerras , "sparclinux@vger.kernel.org" , Alexander Gordeev , Will Deacon , Jonas Bonn , "linux-s390@vger.kernel.org" , "x86@kernel.org" , "linux-csky@vger.kernel.org" , Ingo Molnar , Geert Uytterhoeven , Vasily Gorbik , Heiko Carstens , "openrisc@lists.librecores.org" , Thomas Gleixner , "linux-arm-kernel@lists.infradead.org" , Thomas Bogendoerfer , "linux-mips@vger.kernel.org" , Dinh Nguyen , Sven Schnelle , Andrew Morton , "linuxppc-dev@lists.ozlabs.org" , "David S. Miller" References: <20220603101411.488970-1-anshuman.khandual@arm.com> <20220603101411.488970-3-anshuman.khandual@arm.com> From: Anshuman Khandual In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On 6/3/22 17:55, Christophe Leroy wrote: > > > Le 03/06/2022 à 12:14, Anshuman Khandual a écrit : >> This defines and exports a platform specific custom vm_get_page_prot() via >> subscribing ARCH_HAS_VM_GET_PAGE_PROT. Subsequently all __SXXX and __PXXX >> macros can be dropped which are no longer needed. >> >> Cc: Heiko Carstens >> Cc: Vasily Gorbik >> Cc: linux-s390@vger.kernel.org >> Cc: linux-kernel@vger.kernel.org >> Acked-by: Sven Schnelle >> Acked-by: Alexander Gordeev >> Signed-off-by: Anshuman Khandual >> --- >> arch/s390/Kconfig | 1 + >> arch/s390/include/asm/pgtable.h | 17 ----------------- >> arch/s390/mm/mmap.c | 33 +++++++++++++++++++++++++++++++++ >> 3 files changed, 34 insertions(+), 17 deletions(-) >> >> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig >> index b17239ae7bd4..cdcf678deab1 100644 >> --- a/arch/s390/Kconfig >> +++ b/arch/s390/Kconfig >> @@ -81,6 +81,7 @@ config S390 >> select ARCH_HAS_SYSCALL_WRAPPER >> select ARCH_HAS_UBSAN_SANITIZE_ALL >> select ARCH_HAS_VDSO_DATA >> + select ARCH_HAS_VM_GET_PAGE_PROT >> select ARCH_HAVE_NMI_SAFE_CMPXCHG >> select ARCH_INLINE_READ_LOCK >> select ARCH_INLINE_READ_LOCK_BH >> diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h >> index a397b072a580..c63a05b5368a 100644 >> --- a/arch/s390/include/asm/pgtable.h >> +++ b/arch/s390/include/asm/pgtable.h >> @@ -424,23 +424,6 @@ static inline int is_module_addr(void *addr) >> * implies read permission. >> */ >> /*xwr*/ >> -#define __P000 PAGE_NONE >> -#define __P001 PAGE_RO >> -#define __P010 PAGE_RO >> -#define __P011 PAGE_RO >> -#define __P100 PAGE_RX >> -#define __P101 PAGE_RX >> -#define __P110 PAGE_RX >> -#define __P111 PAGE_RX >> - >> -#define __S000 PAGE_NONE >> -#define __S001 PAGE_RO >> -#define __S010 PAGE_RW >> -#define __S011 PAGE_RW >> -#define __S100 PAGE_RX >> -#define __S101 PAGE_RX >> -#define __S110 PAGE_RWX >> -#define __S111 PAGE_RWX >> >> /* >> * Segment entry (large page) protection definitions. >> diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c >> index d545f5c39f7e..11d75b8d5ec0 100644 >> --- a/arch/s390/mm/mmap.c >> +++ b/arch/s390/mm/mmap.c >> @@ -188,3 +188,36 @@ void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack) >> mm->get_unmapped_area = arch_get_unmapped_area_topdown; >> } >> } >> + >> +pgprot_t vm_get_page_prot(unsigned long vm_flags) >> +{ >> + switch (vm_flags & (VM_READ | VM_WRITE | VM_EXEC | VM_SHARED)) { >> + case VM_NONE: >> + return PAGE_NONE; >> + case VM_READ: >> + case VM_WRITE: >> + case VM_WRITE | VM_READ: >> + return PAGE_RO; >> + case VM_EXEC: >> + case VM_EXEC | VM_READ: >> + case VM_EXEC | VM_WRITE: >> + case VM_EXEC | VM_WRITE | VM_READ: >> + return PAGE_RX; >> + case VM_SHARED: >> + return PAGE_NONE; >> + case VM_SHARED | VM_READ: >> + return PAGE_RO; >> + case VM_SHARED | VM_WRITE: >> + case VM_SHARED | VM_WRITE | VM_READ: >> + return PAGE_RW; >> + case VM_SHARED | VM_EXEC: >> + case VM_SHARED | VM_EXEC | VM_READ: >> + return PAGE_RX; >> + case VM_SHARED | VM_EXEC | VM_WRITE: >> + case VM_SHARED | VM_EXEC | VM_WRITE | VM_READ: >> + return PAGE_RWX; >> + default: >> + BUILD_BUG(); >> + } >> +} >> +EXPORT_SYMBOL(vm_get_page_prot); > > Wasn't it demonstrated in previous discussions that a switch/case is > suboptimal compared to a table cell read ? Right but all these platform patches here were acked from respective platform folks. I assumed that they might have valued the simplicity in switch case statements, while also dropping off the __SXXX/__PXXX macros, which is the final objective. Looks like that assumption was not accurate. > > In order to get rid of the _Sxxx/_Pxxx macros, my preference would go to > having architectures provide their own protection_map[] table, and keep > the generic vm_get_page_prot() for the architectures would don't need a > specific version of it. I will try and rework the patches as suggested. > > This comment applies to all following patches as well.