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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 D4B6BC43381 for ; Fri, 15 Feb 2019 08:11:48 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 96E63218FF for ; Fri, 15 Feb 2019 08:11:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 96E63218FF 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 2CBB48E0002; Fri, 15 Feb 2019 03:11:22 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 2AC2B8E0001; Fri, 15 Feb 2019 03:11:22 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 192C78E0002; Fri, 15 Feb 2019 03:11:22 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from mail-ed1-f71.google.com (mail-ed1-f71.google.com [209.85.208.71]) by kanga.kvack.org (Postfix) with ESMTP id B47668E0001 for ; Fri, 15 Feb 2019 03:11:21 -0500 (EST) Received: by mail-ed1-f71.google.com with SMTP id m25so3559709edp.22 for ; Fri, 15 Feb 2019 00:11:21 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-original-authentication-results:x-gm-message-state:from:subject :to:cc:references:message-id:date:user-agent:mime-version :in-reply-to:content-language:content-transfer-encoding; bh=ZmjmF2pp64kgZvcLy1UzWdAn5K3MvkS5Ruj/r8/274I=; b=SqH3IuVIlEH1EuydgcQrBwThRjKcU/5YDjjzRM9NFz5TppLDNsi4z66dZ/Xa/HEi8j NcVL7He4te1Qbskzo3aOyR5iJZ9euGXEhTYHftxVhIOdQDSTxGqAHnte1QW7VWkulDzx HbsT4lb9+1wpHwWgmkYipZQZpG49/C43JOJsSAegoDh28GtwJiFR8naPL5nBR8SPBe+X 3y4iE1pi6dFWDC5ihFSkSaiPkiN1iEZoF+hlq2b85U6kLds/7krZDTfWwzCBoWPN+gdS nl9SWZ35kSF3r/4N+WlYWHffn3pnL+lwu4jrL00R02ynaYt9L6Eqv29lGptVbnWbXMl+ GvGw== X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of anshuman.khandual@arm.com designates 217.140.101.70 as permitted sender) smtp.mailfrom=anshuman.khandual@arm.com X-Gm-Message-State: AHQUAuaNzDmehktUIB946h0dCTXpAz6Aeb78vVZ5vkRnNlXH1qhk7ypz XEz6cXGF6dPxiT24ymVKLKNEeC8p0xfClPAoYjrJnGP/9T9RhHRzcxKRTUTtHAtx2AuVOppfae+ +4W0+uZaZMmZtO0yOapisyunFO+PRoiEki2M7jOcAU+92Zrdv37vDBeuLu48la8c/lQ== X-Received: by 2002:a05:6402:13cd:: with SMTP id a13mr6674825edx.152.1550218281294; Fri, 15 Feb 2019 00:11:21 -0800 (PST) X-Google-Smtp-Source: AHgI3IZKA87e8XC4v0ROS7dEbBLi3qC3xvHRcg/KEYkBD0BUQLZOBpQRyiF7pAXmTGRGizSJLAFb X-Received: by 2002:a05:6402:13cd:: with SMTP id a13mr6674771edx.152.1550218280402; Fri, 15 Feb 2019 00:11:20 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1550218280; cv=none; d=google.com; s=arc-20160816; b=vY7YZa3S+OA6/CgjKkYidndB+pT9lL0VFGUi8AS3FPfYd95dKrXxQesAtkiWOas2HN 6R77rEY8sHfRC53liLiD0qYtqoARfIJC7pcBO32kHtPOB4W72gYbz0sJ2s1DKcJVU/Z5 mL7hx914fpEJHyI+QJexwsFYrCC+3QaPuNiJF/cSRQe+HWQ97CuxWLVVdk1lD1zSF+NX rijLHd17NhKXP+ibYXOkOwHVEOmKBDicJefH8WKAOwEP9AuNkXBzTshsfpKf3BUEfFOm R0TP4KC2hX2Kv4FcoV7BInQENokN6SrK8/m4vPve52/6WsKTrJUXB7wyvLhnMrGXexB2 xQWQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:content-language:in-reply-to:mime-version :user-agent:date:message-id:references:cc:to:subject:from; bh=ZmjmF2pp64kgZvcLy1UzWdAn5K3MvkS5Ruj/r8/274I=; b=DXoX3hT7kPEbi1bpBn0yu46aOT+aWIdQrHIwLiRvOgdX1uDFruCSiU5AqXqFzKnbsT r03hSl8GG/tKAXW6wvo2yVnF0LWA/yshpQCs+CYXhPUb7V6ERn3la5zQQVk4RP4/8NRX L+Olwt5MMpNF4MoPLvEizXEzYOWXlmZSFPD3QhUtApVYwE/ghBp3cEKEOrnC0O3VcRK6 4MzDT7LSKrsf9EQF1ujwO6rBKH9Hm8rtlHSKIRuldFzpVVmo2UROZELkB0v3F3OiUvo1 2A8nlQtK0OhwBG4ElPPfS/FOMLZ3B/DrAA59xxW4xJu+xnKoRqPMkIYb2koCh51yoUWQ 5ATw== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of anshuman.khandual@arm.com designates 217.140.101.70 as permitted sender) smtp.mailfrom=anshuman.khandual@arm.com Received: from foss.arm.com (foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id w21si2244976eds.29.2019.02.15.00.11.20 for ; Fri, 15 Feb 2019 00:11:20 -0800 (PST) Received-SPF: pass (google.com: domain of anshuman.khandual@arm.com designates 217.140.101.70 as permitted sender) client-ip=217.140.101.70; Authentication-Results: mx.google.com; spf=pass (google.com: domain of anshuman.khandual@arm.com designates 217.140.101.70 as permitted sender) smtp.mailfrom=anshuman.khandual@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id DD745A78; Fri, 15 Feb 2019 00:11:18 -0800 (PST) Received: from [10.162.43.140] (p8cg001049571a15.blr.arm.com [10.162.43.140]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A10BA3F557; Fri, 15 Feb 2019 00:11:15 -0800 (PST) From: Anshuman Khandual Subject: Re: [RFC 1/4] mm: Introduce lazy exec permission setting on a page To: Mike Rapoport Cc: Matthew Wilcox , linux-mm@kvack.org, akpm@linux-foundation.org, mhocko@kernel.org, kirill@shutemov.name, kirill.shutemov@linux.intel.com, vbabka@suse.cz, will.deacon@arm.com, catalin.marinas@arm.com, dave.hansen@intel.com References: <1550045191-27483-1-git-send-email-anshuman.khandual@arm.com> <1550045191-27483-2-git-send-email-anshuman.khandual@arm.com> <20190213131710.GR12668@bombadil.infradead.org> <19b85484-e76b-3ef0-b013-49efa87917ae@arm.com> <20190214090628.GB9063@rapoport-lnx> Message-ID: <8dfa8273-b21d-5f6c-eb3e-7992c6863a07@arm.com> Date: Fri, 15 Feb 2019 13:41:16 +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: <20190214090628.GB9063@rapoport-lnx> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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 02/14/2019 02:36 PM, Mike Rapoport wrote: > On Wed, Feb 13, 2019 at 07:23:18PM +0530, Anshuman Khandual wrote: >> >> >> On 02/13/2019 06:47 PM, Matthew Wilcox wrote: >>> On Wed, Feb 13, 2019 at 01:36:28PM +0530, Anshuman Khandual wrote: >>>> +#ifdef CONFIG_ARCH_SUPPORTS_LAZY_EXEC >>>> +static inline pte_t maybe_mkexec(pte_t entry, struct vm_area_struct *vma) >>>> +{ >>>> + if (unlikely(vma->vm_flags & VM_EXEC)) >>>> + return pte_mkexec(entry); >>>> + return entry; >>>> +} >>>> +#else >>>> +static inline pte_t maybe_mkexec(pte_t entry, struct vm_area_struct *vma) >>>> +{ >>>> + return entry; >>>> +} >>>> +#endif >>> >>>> +++ b/mm/memory.c >>>> @@ -2218,6 +2218,8 @@ static inline void wp_page_reuse(struct vm_fault *vmf) >>>> flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte)); >>>> entry = pte_mkyoung(vmf->orig_pte); >>>> entry = maybe_mkwrite(pte_mkdirty(entry), vma); >>>> + if (vmf->flags & FAULT_FLAG_INSTRUCTION) >>>> + entry = maybe_mkexec(entry, vma); >>> >>> I don't understand this bit. We have a fault based on an instruction >>> fetch. But we're only going to _maybe_ set the exec bit? Why not call >>> pte_mkexec() unconditionally? >> >> Because the arch might not have subscribed to this in which case the fall >> back function does nothing and return the same entry. But in case this is >> enabled it also checks for VMA exec flag (VM_EXEC) before calling into >> pte_mkexec() something similar to existing maybe_mkwrite(). > > Than why not pass vmf->flags to maybe_mkexec() so that only arches > subscribed to this will have the check for 'flags & FAULT_FLAG_INSTRUCTION' ? Right it can help remove couple of instructions from un-subscribing archs.