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 24B9DC433F5 for ; Mon, 25 Apr 2022 05:52:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236115AbiDYFza (ORCPT ); Mon, 25 Apr 2022 01:55:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56638 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231330AbiDYFzW (ORCPT ); Mon, 25 Apr 2022 01:55:22 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 1694B36318 for ; Sun, 24 Apr 2022 22:52:17 -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 ACB7F1FB; Sun, 24 Apr 2022 22:52:16 -0700 (PDT) Received: from [10.163.40.250] (unknown [10.163.40.250]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5DF9A3F774; Sun, 24 Apr 2022 22:52:06 -0700 (PDT) Message-ID: <0f4de9db-1e36-b9d8-bd94-6e3ec3842940@arm.com> Date: Mon, 25 Apr 2022 11:22:58 +0530 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH -next v5 3/5] mm: page_table_check: add hooks to public helpers Content-Language: en-US To: Tong Tiangen , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Pasha Tatashin , Andrew Morton , Catalin Marinas , Will Deacon , Paul Walmsley , Palmer Dabbelt , Albert Ou Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-riscv@lists.infradead.org, Kefeng Wang , Guohanjun References: <20220421082042.1167967-1-tongtiangen@huawei.com> <20220421082042.1167967-4-tongtiangen@huawei.com> <7fc56f41-a3c2-76be-7a20-dda392f3c4fc@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-kernel@vger.kernel.org On 4/24/22 09:40, Tong Tiangen wrote: > > > 在 2022/4/22 14:05, Anshuman Khandual 写道: >> >> >> On 4/21/22 13:50, Tong Tiangen wrote: >>> Move ptep_clear() to the include/linux/pgtable.h and add page table check >>> relate hooks to some helpers, it's prepare for support page table check >>> feature on new architecture. >> >> Could instrumenting generic page table helpers (fallback instances when its >> corresponding __HAVE_ARCH_XXX is not defined on the platform), might add all >> the page table check hooks into paths on platforms which have not subscribed >> ARCH_SUPPORTS_PAGE_TABLE_CHECK in the first place ? Although these looks have >> !CONFIG_PAGE_TABLE_CHECK fallback stubs in the header, hence a build problem >> gets avoided. > > Right, build problems are avoided by fallback stubs in the header file. Although there might not be a build problem as such, but should non subscribing platforms get their page table helpers instrumented with page table check hooks in the first place ? The commit message should address these questions. > >> >>> >>> Signed-off-by: Tong Tiangen >>> Acked-by: Pasha Tatashin >>> --- >>>   arch/x86/include/asm/pgtable.h | 10 ---------- >>>   include/linux/pgtable.h        | 26 ++++++++++++++++++-------- >>>   2 files changed, 18 insertions(+), 18 deletions(-) >>> >>> diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h >>> index 564abe42b0f7..51cd39858f81 100644 >>> --- a/arch/x86/include/asm/pgtable.h >>> +++ b/arch/x86/include/asm/pgtable.h >>> @@ -1073,16 +1073,6 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm, >>>       return pte; >>>   } >>>   -#define __HAVE_ARCH_PTEP_CLEAR >> >> AFICS X86 is the only platform subscribing __HAVE_ARCH_PTEP_CLEAR. Hence if >> this is getting dropped for generic ptep_clear(), then no need to add back >> #ifnded __HAVE_ARCH_PTEP_CLEAR construct. Generic ptep_clear() is the only >> definition for all platforms ? >> >> Also if this patch is trying to drop off __HAVE_ARCH_PTEP_CLEAR along with >> other page table check related changes, it needs to be done via a separate >> patch instead. > > Agreed. > IMO, this fix can be patched later. > >> >>> -static inline void ptep_clear(struct mm_struct *mm, unsigned long addr, >>> -                  pte_t *ptep) >>> -{ >>> -    if (IS_ENABLED(CONFIG_PAGE_TABLE_CHECK)) >>> -        ptep_get_and_clear(mm, addr, ptep); >>> -    else >>> -        pte_clear(mm, addr, ptep); >>> -} >>> - >>>   #define __HAVE_ARCH_PTEP_SET_WRPROTECT >>>   static inline void ptep_set_wrprotect(struct mm_struct *mm, >>>                         unsigned long addr, pte_t *ptep) >>> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h >>> index 49ab8ee2d6d7..10d2d91edf20 100644 >>> --- a/include/linux/pgtable.h >>> +++ b/include/linux/pgtable.h >>> @@ -12,6 +12,7 @@ >>>   #include >>>   #include >>>   #include >>> +#include >>>     #if 5 - defined(__PAGETABLE_P4D_FOLDED) - defined(__PAGETABLE_PUD_FOLDED) - \ >>>       defined(__PAGETABLE_PMD_FOLDED) != CONFIG_PGTABLE_LEVELS >>> @@ -272,14 +273,6 @@ static inline bool arch_has_hw_pte_young(void) >>>   } >>>   #endif >>>   -#ifndef __HAVE_ARCH_PTEP_CLEAR >>> -static inline void ptep_clear(struct mm_struct *mm, unsigned long addr, >>> -                  pte_t *ptep) >>> -{ >>> -    pte_clear(mm, addr, ptep); >>> -} >>> -#endif >>> - >>>   #ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR >>>   static inline pte_t ptep_get_and_clear(struct mm_struct *mm, >>>                          unsigned long address, >>> @@ -287,10 +280,22 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm, >>>   { >>>       pte_t pte = *ptep; >>>       pte_clear(mm, address, ptep); >>> +    page_table_check_pte_clear(mm, address, pte); >>>       return pte; >>>   } >>>   #endif >>>   +#ifndef __HAVE_ARCH_PTEP_CLEAR >>> +static inline void ptep_clear(struct mm_struct *mm, unsigned long addr, >>> +                  pte_t *ptep) >>> +{ >>> +    if (IS_ENABLED(CONFIG_PAGE_TABLE_CHECK)) >>> +        ptep_get_and_clear(mm, addr, ptep); >>> +    else >>> +        pte_clear(mm, addr, ptep); >> >> Could not this be reworked to avoid IS_ENABLED() ? This is confusing. If the page >> table hooks can be added to all potential page table paths via generic helpers, >> irrespective of CONFIG_PAGE_TABLE_CHECK option, there is no rationale for doing >> a IS_ENABLED() check here. >> > > From the perspective of code logic, we need to check the pte before being cleared. Whether pte check is required depends on IS_ENABLED(). > > Are there any suggestions for better implementation? But other generic page table helpers already have page table check hooks instrumented without IS_ENABLED() checks, then why this is any different. > > Thank you, > Tong. > >>> +} >>> +#endif >>> + >>>   #ifndef __HAVE_ARCH_PTEP_GET >>>   static inline pte_t ptep_get(pte_t *ptep) >>>   { >>> @@ -360,7 +365,10 @@ static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm, >>>                           pmd_t *pmdp) >>>   { >>>       pmd_t pmd = *pmdp; >>> + >>>       pmd_clear(pmdp); >>> +    page_table_check_pmd_clear(mm, address, pmd); >>> + >>>       return pmd; >>>   } >>>   #endif /* __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR */ >>> @@ -372,6 +380,8 @@ static inline pud_t pudp_huge_get_and_clear(struct mm_struct *mm, >>>       pud_t pud = *pudp; >>>         pud_clear(pudp); >>> +    page_table_check_pud_clear(mm, address, pud); >>> + >>>       return pud; >>>   } >>>   #endif /* __HAVE_ARCH_PUDP_HUGE_GET_AND_CLEAR */ >> .