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 X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 143EAC28CBC for ; Wed, 6 May 2020 10:22:18 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9B1812068E for ; Wed, 6 May 2020 10:22:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9B1812068E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id EE5EB8E0005; Wed, 6 May 2020 06:22:16 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E96648E0003; Wed, 6 May 2020 06:22:16 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D84588E0005; Wed, 6 May 2020 06:22:16 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0022.hostedemail.com [216.40.44.22]) by kanga.kvack.org (Postfix) with ESMTP id BE8868E0003 for ; Wed, 6 May 2020 06:22:16 -0400 (EDT) Received: from smtpin30.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 8CAF6824999B for ; Wed, 6 May 2020 10:22:16 +0000 (UTC) X-FDA: 76785904272.30.trip68_4e04dd7237f56 X-HE-Tag: trip68_4e04dd7237f56 X-Filterd-Recvd-Size: 3232 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf20.hostedemail.com (Postfix) with ESMTP for ; Wed, 6 May 2020 10:22:16 +0000 (UTC) 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 239E730E; Wed, 6 May 2020 03:22:15 -0700 (PDT) Received: from [10.163.71.196] (unknown [10.163.71.196]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E9A7E3F71F; Wed, 6 May 2020 03:22:12 -0700 (PDT) Subject: Re: [PATCH V2 1/3] arm64/mm: Drop __HAVE_ARCH_HUGE_PTEP_GET To: Will Deacon Cc: linux-mm@kvack.org, akpm@linux-foundation.org, Catalin Marinas , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <1588745534-24418-1-git-send-email-anshuman.khandual@arm.com> <1588745534-24418-2-git-send-email-anshuman.khandual@arm.com> <20200506074315.GD7021@willie-the-truck> From: Anshuman Khandual Message-ID: <14911279-f800-a781-a4fd-de43215aa909@arm.com> Date: Wed, 6 May 2020 15:51:42 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20200506074315.GD7021@willie-the-truck> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 05/06/2020 01:13 PM, Will Deacon wrote: > On Wed, May 06, 2020 at 11:42:12AM +0530, Anshuman Khandual wrote: >> Platform specific huge_ptep_get() is required only when fetching the huge >> PTE involves more than just dereferencing the page table pointer. This is >> not the case on arm64 platform. Hence huge_ptep_pte() can be dropped along >> with it's __HAVE_ARCH_HUGE_PTEP_GET subscription. >> >> Cc: Catalin Marinas >> Cc: Will Deacon >> Cc: Andrew Morton >> Cc: linux-arm-kernel@lists.infradead.org >> Cc: linux-mm@kvack.org >> Cc: linux-kernel@vger.kernel.org >> Signed-off-by: Anshuman Khandual >> --- >> arch/arm64/include/asm/hugetlb.h | 6 ------ >> 1 file changed, 6 deletions(-) >> >> diff --git a/arch/arm64/include/asm/hugetlb.h b/arch/arm64/include/asm/hugetlb.h >> index 2eb6c234d594..b88878ddc88b 100644 >> --- a/arch/arm64/include/asm/hugetlb.h >> +++ b/arch/arm64/include/asm/hugetlb.h >> @@ -17,12 +17,6 @@ >> extern bool arch_hugetlb_migration_supported(struct hstate *h); >> #endif >> >> -#define __HAVE_ARCH_HUGE_PTEP_GET >> -static inline pte_t huge_ptep_get(pte_t *ptep) >> -{ >> - return READ_ONCE(*ptep); >> -} > > Hmm, I'm nervous about dropping the READ_ONCE() here. We added them after > running into page-table issues with THP [1] and it's really important to > use them consistently to avoid hitting that again. > > If the generic code used READ_ONCE(), I'd be happy to switch to it. Sure, will add READ_ONCE() in the generic huge_ptep_get(). AFAICS it should not cause any problem for other platforms (but let me know otherwise). > > Will > > [1] https://lore.kernel.org/lkml/1506527369-19535-1-git-send-email-will.deacon@arm.com/ >