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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1B837C433F5 for ; Thu, 5 May 2022 06:47:02 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9CF106B0071; Thu, 5 May 2022 02:47:01 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9575B6B0073; Thu, 5 May 2022 02:47:01 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7F84A6B0074; Thu, 5 May 2022 02:47:01 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 6D2B26B0071 for ; Thu, 5 May 2022 02:47:01 -0400 (EDT) Received: from smtpin11.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 4BBE5611E8 for ; Thu, 5 May 2022 06:47:01 +0000 (UTC) X-FDA: 79430757042.11.99BBE9A Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by imf28.hostedemail.com (Postfix) with ESMTP id 1FDB6C0087 for ; Thu, 5 May 2022 06:46:44 +0000 (UTC) Received: from kwepemi500012.china.huawei.com (unknown [172.30.72.57]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4Kv4310yQ8zfbF5; Thu, 5 May 2022 14:45:49 +0800 (CST) Received: from kwepemm600017.china.huawei.com (7.193.23.234) by kwepemi500012.china.huawei.com (7.221.188.12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Thu, 5 May 2022 14:46:53 +0800 Received: from [10.174.179.234] (10.174.179.234) by kwepemm600017.china.huawei.com (7.193.23.234) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Thu, 5 May 2022 14:46:52 +0800 Message-ID: <3f0439c7-9c25-b83a-58dd-9c3d638b9236@huawei.com> Date: Thu, 5 May 2022 14:46:51 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: [PATCH -next v6 5/6] arm64/mm: Enable ARCH_SUPPORTS_PAGE_TABLE_CHECK To: Catalin Marinas CC: Anshuman Khandual , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , , "H. Peter Anvin" , Pasha Tatashin , Andrew Morton , Will Deacon , Paul Walmsley , Palmer Dabbelt , Albert Ou , , , , , Kefeng Wang , Guohanjun References: <20220426081036.1374452-1-tongtiangen@huawei.com> <20220426081036.1374452-6-tongtiangen@huawei.com> <80f6c347-db5d-8836-bc79-60c7b2a6eed8@huawei.com> From: Tong Tiangen In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.179.234] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To kwepemm600017.china.huawei.com (7.193.23.234) X-CFilter-Loop: Reflected X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 1FDB6C0087 X-Stat-Signature: pezbf1y46359dm4ewswtcjqun3zkkjh6 Authentication-Results: imf28.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf28.hostedemail.com: domain of tongtiangen@huawei.com designates 45.249.212.187 as permitted sender) smtp.mailfrom=tongtiangen@huawei.com X-Rspam-User: X-HE-Tag: 1651733204-955027 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: 在 2022/5/5 1:26, Catalin Marinas 写道: > On Tue, May 03, 2022 at 09:13:20AM +0800, Tong Tiangen wrote: >> 在 2022/4/29 14:18, Anshuman Khandual 写道: >>> On 4/26/22 13:40, Tong Tiangen wrote: >>>> @@ -884,7 +928,11 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm, >>>> static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm, >>>> unsigned long address, pmd_t *pmdp) >>>> { >>>> - return pte_pmd(ptep_get_and_clear(mm, address, (pte_t *)pmdp)); >>>> + pmd_t pmd = pte_pmd(__pte(xchg_relaxed(&pte_val(*(pte_t *)pmdp), 0))); >>> >>> Why there is any change here ? Why not just the following instead, like what you did >>> in ptep_get_and_clear() above. The page table entry return value here just needs to >>> be preserved for subsequent page table check helpers. >>> >>> pmd_t pmd = pte_pmd(ptep_get_and_clear(mm, address, (pte_t *)pmdp)); >> >> The purpose of what I do here is to avoid doing page_table_check_pte_clear() >> in ptep_get_and_clear(). there is no functional change here. > > I'm fine with using xchg here but I'd go for pmd_val directly, no need > for conversion to pte_t: > > pmd_t pmd = __pmd(xchg_relaxed(&pmd_val(*pmdp), 0)); > OK, This implementation is good and avoids redundant conversion, will fix it next version. Thanks, Tong.