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 5B947C433F5 for ; Wed, 4 May 2022 17:26:55 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B7C1B6B0071; Wed, 4 May 2022 13:26:54 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B2A676B0073; Wed, 4 May 2022 13:26:54 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9F1DB6B0074; Wed, 4 May 2022 13:26:54 -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 8F8C46B0071 for ; Wed, 4 May 2022 13:26:54 -0400 (EDT) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 588A62A8A6 for ; Wed, 4 May 2022 17:26:54 +0000 (UTC) X-FDA: 79428740748.30.8D3D219 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by imf20.hostedemail.com (Postfix) with ESMTP id 7CC451C00A1 for ; Wed, 4 May 2022 17:26:47 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id E7203B8279D; Wed, 4 May 2022 17:26:51 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 13756C385A4; Wed, 4 May 2022 17:26:46 +0000 (UTC) Date: Wed, 4 May 2022 18:26:43 +0100 From: Catalin Marinas To: Tong Tiangen Cc: Anshuman Khandual , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Pasha Tatashin , Andrew Morton , Will Deacon , Paul Walmsley , Palmer Dabbelt , Albert Ou , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-riscv@lists.infradead.org, Kefeng Wang , Guohanjun Subject: Re: [PATCH -next v6 5/6] arm64/mm: Enable ARCH_SUPPORTS_PAGE_TABLE_CHECK Message-ID: References: <20220426081036.1374452-1-tongtiangen@huawei.com> <20220426081036.1374452-6-tongtiangen@huawei.com> <80f6c347-db5d-8836-bc79-60c7b2a6eed8@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <80f6c347-db5d-8836-bc79-60c7b2a6eed8@huawei.com> X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 7CC451C00A1 X-Stat-Signature: k4wa4x3s9yth97w53f1wbtyt7r34mtt3 Authentication-Results: imf20.hostedemail.com; dkim=none; dmarc=fail reason="SPF not aligned (relaxed), No valid DKIM" header.from=arm.com (policy=none); spf=pass (imf20.hostedemail.com: domain of cmarinas@kernel.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=cmarinas@kernel.org X-HE-Tag: 1651685207-970657 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 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)); -- Catalin