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 D1045C433EF for ; Mon, 18 Jul 2022 19:37:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236193AbiGRThT (ORCPT ); Mon, 18 Jul 2022 15:37:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57378 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236157AbiGRThK (ORCPT ); Mon, 18 Jul 2022 15:37:10 -0400 Received: from mail-pj1-x1031.google.com (mail-pj1-x1031.google.com [IPv6:2607:f8b0:4864:20::1031]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 658082CCB9 for ; Mon, 18 Jul 2022 12:37:09 -0700 (PDT) Received: by mail-pj1-x1031.google.com with SMTP id a15so12753123pjs.0 for ; Mon, 18 Jul 2022 12:37:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=ZFfNYrVG625GOSA+id1AogN2HiBF2G/dud76HkUGe+4=; b=DuOhKFmRzGfZbq1nE2NE6Kc5a1/zJpTjh2RvqjQrCWls/7Qhm59F3Q5qnZAqPiZzON HTPLLExPZor3+WUD0GCeFJpaZ9HYJzT2HyRhOUdXKPSxPoB6NcCCp6BaC0PUnMozc1Yt 7yR/B8zLzmfdp4wBCIwoubwwq+IB152Z6aXNEBRtKOMqAeRb0Yg89EaxtZKRLj96Zhk2 zoX+JoTOX8z/qePogfLcdbultYnUpTJzA0NIOrLiUF3n+b/B8dbqeFNxtjocuKqlEg9I gVwTOuaGbUDx39ekLwLxOUStg09K/QpEk4bRVNpBu1NY3eLXRtkHF8N04DDoJYpcUW4c qdtw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=ZFfNYrVG625GOSA+id1AogN2HiBF2G/dud76HkUGe+4=; b=Nti7WPuVxm8TeHVNyBgzYwmxLHmfDCvVoDS3GKG8ndpeF/h5J9GGDhTlsBwhvWcl85 HlYg11vGOjswxZA07Gqe9fYdaSJYx7R/4qtEJ9VMd8sojEyIqVXhHm+XUyzNoSgoeqP5 xED4uYiRkcuCK6Pb6aXDy1GQPhMTAntVQNVv08+moqU9BYv9fsmjxOjnN4kX4EWHHUuV epoNUUmty2zy0NrUJXSPDy1dhSohlXRMnUx8Eqb3g2Siol8BD/N3O2nM317ZUu/7N4pe HTVMTpi29SwIJzn7dd8b6+sfJcbJUY8t9Ceq+IyWjv4QDuUpWgKQa52TSOMSlQP9kXTl klpA== X-Gm-Message-State: AJIora/a0d0q8OR+O44L/M8CFk59oTDSHFn2w9dgtwyJod46sQX01FNk 8yilkL9xY3r6u91jd01gi0s= X-Google-Smtp-Source: AGRyM1vEHCEomLrXWGc5eN5sitXXmIDRxEROcYfVCHE3CQXw0PbDpM+yh+ClwMd2ENoAaXz/XYUQHw== X-Received: by 2002:a17:90a:9f8d:b0:1f0:253e:3ecf with SMTP id o13-20020a17090a9f8d00b001f0253e3ecfmr41557002pjp.33.1658173028683; Mon, 18 Jul 2022 12:37:08 -0700 (PDT) Received: from sc2-haas01-esx0118.eng.vmware.com ([66.170.99.1]) by smtp.gmail.com with ESMTPSA id q6-20020a170902a3c600b0016bc4a6ce28sm9907887plb.98.2022.07.18.12.37.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 18 Jul 2022 12:37:08 -0700 (PDT) From: Nadav Amit X-Google-Original-From: Nadav Amit To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Andrew Morton , Mike Rapoport , Axel Rasmussen , Nadav Amit , Andrea Arcangeli , Andrew Cooper , Andy Lutomirski , Dave Hansen , David Hildenbrand , Peter Xu , Peter Zijlstra , Thomas Gleixner , Will Deacon , Yu Zhao , Nick Piggin Subject: [RFC PATCH 04/14] mm/mprotect: preserve write with MM_CP_TRY_CHANGE_WRITABLE Date: Mon, 18 Jul 2022 05:02:02 -0700 Message-Id: <20220718120212.3180-5-namit@vmware.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220718120212.3180-1-namit@vmware.com> References: <20220718120212.3180-1-namit@vmware.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Nadav Amit When MM_CP_TRY_CHANGE_WRITABLE is used, change_pte_range() tries to set PTEs as writable. Yet, writable PTEs might still become read-only, due to various limitations of the logic that determines whether a PTE can become writable (see can_change_pte_writable()). Anyhow, it is much easier to keep the writable bit set when MM_CP_TRY_CHANGE_WRITABLE is used than to first clear it and then figure out whether it can be set again. Preserve the write-bit when MM_CP_TRY_CHANGE_WRITABLE is used, similarly to the way it is done with NUMA. Cc: Andrea Arcangeli Cc: Andrew Cooper Cc: Andrew Morton Cc: Andy Lutomirski Cc: Dave Hansen Cc: David Hildenbrand Cc: Peter Xu Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Will Deacon Cc: Yu Zhao Cc: Nick Piggin Signed-off-by: Nadav Amit --- mm/mprotect.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/mm/mprotect.c b/mm/mprotect.c index da5b9bf8204f..92bfb17dcb8a 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -84,6 +84,7 @@ static unsigned long change_pte_range(struct mmu_gather *tlb, bool uffd_wp = cp_flags & MM_CP_UFFD_WP; bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE; bool will_need = cp_flags & MM_CP_WILL_NEED; + bool try_change_writable = cp_flags & MM_CP_TRY_CHANGE_WRITABLE; tlb_change_page_size(tlb, PAGE_SIZE); @@ -114,7 +115,8 @@ static unsigned long change_pte_range(struct mmu_gather *tlb, oldpte = *pte; if (pte_present(oldpte)) { pte_t ptent; - bool preserve_write = prot_numa && pte_write(oldpte); + bool preserve_write = (prot_numa || try_change_writable) && + pte_write(oldpte); /* * Avoid trapping faults against the zero or KSM @@ -190,8 +192,7 @@ static unsigned long change_pte_range(struct mmu_gather *tlb, * example, if a PTE is already dirty and no other * COW or special handling is required. */ - if ((cp_flags & MM_CP_TRY_CHANGE_WRITABLE) && - !pte_write(ptent) && + if (try_change_writable && !pte_write(ptent) && can_change_pte_writable(vma, addr, ptent)) { ptent = pte_mkwrite(ptent); if (will_need) -- 2.25.1