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=-7.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 EC535C433E0 for ; Tue, 2 Feb 2021 14:47:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AD72164F4D for ; Tue, 2 Feb 2021 14:47:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232277AbhBBOrZ (ORCPT ); Tue, 2 Feb 2021 09:47:25 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:59655 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234623AbhBBOgT (ORCPT ); Tue, 2 Feb 2021 09:36:19 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612276493; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=DMQGIZBX3ZSdULucq6YnujqHSWIcTSgvTL7Om1Dz16I=; b=TB4f54GA6of7/fhHlL/DuK168L4SCX0eFlv9Nj8+BS15mujoNNh6Zh3wB3ferDM6D4LsUp RzxQbicNJa2cuAV1vIX2jC3Yl57abYxTir8Gadw03l/KFjyRH7KGgjWtMYBNIb+ZwZ/p1A F/GWWPlOnXmMZeSqeqhRJ/9dts0hSrg= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-464-dkvrsbKJMeCl98dqyoVbLw-1; Tue, 02 Feb 2021 09:34:48 -0500 X-MC-Unique: dkvrsbKJMeCl98dqyoVbLw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0E886184DBF0; Tue, 2 Feb 2021 14:34:44 +0000 (UTC) Received: from [10.36.114.148] (ovpn-114-148.ams2.redhat.com [10.36.114.148]) by smtp.corp.redhat.com (Postfix) with ESMTP id 505D15D9C6; Tue, 2 Feb 2021 14:34:36 +0000 (UTC) Subject: Re: [PATCH v16 07/11] secretmem: use PMD-size pages to amortize direct map fragmentation To: Michal Hocko Cc: Mike Rapoport , James Bottomley , Andrew Morton , Alexander Viro , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Catalin Marinas , Christopher Lameter , Dan Williams , Dave Hansen , Elena Reshetova , "H. Peter Anvin" , Ingo Molnar , "Kirill A. Shutemov" , Matthew Wilcox , Mark Rutland , Mike Rapoport , Michael Kerrisk , Palmer Dabbelt , Paul Walmsley , Peter Zijlstra , Rick Edgecombe , Roman Gushchin , Shakeel Butt , Shuah Khan , Thomas Gleixner , Tycho Andersen , Will Deacon , linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-nvdimm@lists.01.org, linux-riscv@lists.infradead.org, x86@kernel.org, Hagen Paul Pfeifer , Palmer Dabbelt References: <73738cda43236b5ac2714e228af362b67a712f5d.camel@linux.ibm.com> <6de6b9f9c2d28eecc494e7db6ffbedc262317e11.camel@linux.ibm.com> <20210202124857.GN242749@kernel.org> <6653288a-dd02-f9de-ef6a-e8d567d71d53@redhat.com> <211f0214-1868-a5be-9428-7acfc3b73993@redhat.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <95625b83-f7e2-b27a-2b99-d231338047fb@redhat.com> Date: Tue, 2 Feb 2021 15:34:29 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On 02.02.21 15:32, Michal Hocko wrote: > On Tue 02-02-21 15:26:20, David Hildenbrand wrote: >> On 02.02.21 15:22, Michal Hocko wrote: >>> On Tue 02-02-21 15:12:21, David Hildenbrand wrote: >>> [...] >>>> I think secretmem behaves much more like longterm GUP right now >>>> ("unmigratable", "lifetime controlled by user space", "cannot go on >>>> CMA/ZONE_MOVABLE"). I'd either want to reasonably well control/limit it or >>>> make it behave more like mlocked pages. >>> >>> I thought I have already asked but I must have forgotten. Is there any >>> actual reason why the memory is not movable? Timing attacks? >> >> I think the reason is simple: no direct map, no copying of memory. > > This is an implementation detail though and not something terribly hard > to add on top later on. I was more worried there would be really > fundamental reason why this is not possible. E.g. security implications. I don't remember all the details. Let's see what Mike thinks regarding migration (e.g., security concerns). -- Thanks, David / dhildenb