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=-9.9 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, 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 32742C43461 for ; Tue, 8 Sep 2020 10:18:47 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9FE73216C4 for ; Tue, 8 Sep 2020 10:18:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9FE73216C4 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 B99586B0055; Tue, 8 Sep 2020 06:18:45 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B48F06B005A; Tue, 8 Sep 2020 06:18:45 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A60346B005C; Tue, 8 Sep 2020 06:18:45 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0096.hostedemail.com [216.40.44.96]) by kanga.kvack.org (Postfix) with ESMTP id 912006B0055 for ; Tue, 8 Sep 2020 06:18:45 -0400 (EDT) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 5F3F68248047 for ; Tue, 8 Sep 2020 10:18:45 +0000 (UTC) X-FDA: 77239495410.27.smile86_5e0ff0f270d4 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin27.hostedemail.com (Postfix) with ESMTP id 2E29C3D668 for ; Tue, 8 Sep 2020 10:18:45 +0000 (UTC) X-HE-Tag: smile86_5e0ff0f270d4 X-Filterd-Recvd-Size: 4160 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf41.hostedemail.com (Postfix) with ESMTP for ; Tue, 8 Sep 2020 10:18:44 +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 B616631B; Tue, 8 Sep 2020 03:18:43 -0700 (PDT) Received: from [10.163.71.211] (unknown [10.163.71.211]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 80B453F66E; Tue, 8 Sep 2020 03:18:40 -0700 (PDT) Subject: Re: [PATCH 1/2] arm64/mm: Change THP helpers to comply with generic MM semantics To: Catalin Marinas Cc: linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, will@kernel.org, akpm@linux-foundation.org, Mark Rutland , Marc Zyngier , Suzuki Poulose , linux-kernel@vger.kernel.org References: <1597655984-15428-1-git-send-email-anshuman.khandual@arm.com> <1597655984-15428-2-git-send-email-anshuman.khandual@arm.com> <20200903165631.GC31409@gaia> From: Anshuman Khandual Message-ID: Date: Tue, 8 Sep 2020 15:48:08 +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: <20200903165631.GC31409@gaia> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 2E29C3D668 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 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 09/03/2020 10:26 PM, Catalin Marinas wrote: > On Mon, Aug 17, 2020 at 02:49:43PM +0530, Anshuman Khandual wrote: >> pmd_present() and pmd_trans_huge() are expected to behave in the following >> manner during various phases of a given PMD. It is derived from a previous >> detailed discussion on this topic [1] and present THP documentation [2]. >> >> pmd_present(pmd): >> >> - Returns true if pmd refers to system RAM with a valid pmd_page(pmd) >> - Returns false if pmd does not refer to system RAM - Invalid pmd_page(pmd) > > The second bullet doesn't make much sense. If you have a pmd mapping of > some I/O memory, pmd_present() still returns true (as does > pte_present()). Derived this from an earlier discussion (https://lkml.org/lkml/2018/10/17/231) but current representation here might not be accurate. Would this be any better ? pmd_present(pmd): - Returns true if pmd refers to system RAM with a valid pmd_page(pmd) - Returns false if pmd refers to a migration or swap entry > >> diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h >> index 4d867c6446c4..28792fdd9627 100644 >> --- a/arch/arm64/include/asm/pgtable-prot.h >> +++ b/arch/arm64/include/asm/pgtable-prot.h >> @@ -19,6 +19,13 @@ >> #define PTE_DEVMAP (_AT(pteval_t, 1) << 57) >> #define PTE_PROT_NONE (_AT(pteval_t, 1) << 58) /* only when !PTE_VALID */ >> >> +/* >> + * This help indicate that the entry is present i.e pmd_page() > > Nit: add another . after i.e Will fix. > >> + * still points to a valid huge page in memory even if the pmd >> + * has been invalidated. >> + */ >> +#define PMD_PRESENT_INVALID (_AT(pteval_t, 1) << 59) /* only when !PMD_SECT_VALID */ >> + >> #ifndef __ASSEMBLY__ >> >> #include >> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h >> index d5d3fbe73953..7aa69cace784 100644 >> --- a/arch/arm64/include/asm/pgtable.h >> +++ b/arch/arm64/include/asm/pgtable.h >> @@ -145,6 +145,18 @@ static inline pte_t set_pte_bit(pte_t pte, pgprot_t prot) >> return pte; >> } >> >> +static inline pmd_t clr_pmd_bit(pmd_t pmd, pgprot_t prot) >> +{ >> + pmd_val(pmd) &= ~pgprot_val(prot); >> + return pmd; >> +} > > Could you use clear_pmd_bit (instead of clr) for consistency with > clear_pte_bit()? Sure, will do. > > It would be good if the mm folk can do a sanity check on the assumptions > about pmd_present/pmdp_invalidate/pmd_trans_huge. > > The patch looks fine to me otherwise, feel free to add: > > Reviewed-by: Catalin Marinas >