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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 B2A68C433DB for ; Tue, 2 Feb 2021 14:34:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8902664DD6 for ; Tue, 2 Feb 2021 14:34:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234387AbhBBOeV (ORCPT ); Tue, 2 Feb 2021 09:34:21 -0500 Received: from mx2.suse.de ([195.135.220.15]:45390 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234568AbhBBOdF (ORCPT ); Tue, 2 Feb 2021 09:33:05 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1612276338; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ZY7R/A8eLGtcqtBTwPz4dc8E6975FZbZj6rab/rk/co=; b=j08LbR+/N4gscwMe9/vv1y6TbSr6g+uI8Fvmd6aUiZN3eXaYwuKCYZD1LwoDENfRkxwGU0 412GY/gqoJEVKSXG9cJ4ADonbDGXxcU99oWydp5Rm3Y/nVMao0u9sPUOYRoKgo3QRhPEJy MTJSdg+5u8XcNBah4K1e9Bay/Y5Jdaw= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 7D39BAD78; Tue, 2 Feb 2021 14:32:18 +0000 (UTC) Date: Tue, 2 Feb 2021 15:32:16 +0100 From: Michal Hocko To: David Hildenbrand 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 Subject: Re: [PATCH v16 07/11] secretmem: use PMD-size pages to amortize direct map fragmentation Message-ID: 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. -- Michal Hocko SUSE Labs