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 1715FC433EF for ; Wed, 4 May 2022 18:07:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1376690AbiEDSKf (ORCPT ); Wed, 4 May 2022 14:10:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55704 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1359530AbiEDSKH (ORCPT ); Wed, 4 May 2022 14:10:07 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AD9AE5A143 for ; Wed, 4 May 2022 10:26:51 -0700 (PDT) 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 dfw.source.kernel.org (Postfix) with ESMTPS id 4776560A27 for ; 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> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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