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=-6.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 AEA76C43462 for ; Mon, 17 May 2021 07:23:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 935D6611BF for ; Mon, 17 May 2021 07:23:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235239AbhEQHY5 (ORCPT ); Mon, 17 May 2021 03:24:57 -0400 Received: from mail.kernel.org ([198.145.29.99]:54224 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230339AbhEQHYn (ORCPT ); Mon, 17 May 2021 03:24:43 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 5E2C3611BF; Mon, 17 May 2021 07:23:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1621236207; bh=amReGMStusi8xn7FAECc6Whc3fPD7LuG3b6+xADdY7M=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=tdRnG7f8obysw+K28IshiY9r+18IQ1tTvDIIZzARqpPv8mn+ML38PW74E0CX/ofM1 lH6pTkkY5oaht2o74BmWs/L5cRTvCHKxgeuP4jlFuWVFCF97iHrjOxSm63DzM1+DLM 1Lt2mIb6RklOXBbNwT8EFBOEFDI0quAKtHVOhSk40zR+fT+bXp9P4dQI/i7dt6KsqW i1EeofYd4+AfTy3Bm/k+ha4JFLM3skrOayJ1PRDU9e6OwKoW/gcpiHeHcQCbsChuuw eqw8dBOD6kfdNYVMzKFpdKGTDDpXVdsVBQ+yiaI5bgEAr6nOfPYGv21bcodQb5kVaQ lUziwbXpWVN1w== Date: Mon, 17 May 2021 10:23:09 +0300 From: Mike Rapoport To: David Hildenbrand Cc: Andrew Morton , Alexander Viro , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Catalin Marinas , Christopher Lameter , Dan Williams , Dave Hansen , Elena Reshetova , "H. Peter Anvin" , Hagen Paul Pfeifer , Ingo Molnar , James Bottomley , Kees Cook , "Kirill A. Shutemov" , Matthew Wilcox , Matthew Garrett , Mark Rutland , Michal Hocko , Mike Rapoport , Michael Kerrisk , Palmer Dabbelt , Palmer Dabbelt , Paul Walmsley , Peter Zijlstra , "Rafael J. Wysocki" , Rick Edgecombe , Roman Gushchin , Shakeel Butt , Shuah Khan , Thomas Gleixner , Tycho Andersen , Will Deacon , Yury Norov , 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 Subject: Re: [PATCH v19 5/8] mm: introduce memfd_secret system call to create "secret" memory areas Message-ID: References: <20210513184734.29317-1-rppt@kernel.org> <20210513184734.29317-6-rppt@kernel.org> 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-fsdevel@vger.kernel.org On Fri, May 14, 2021 at 10:50:55AM +0200, David Hildenbrand wrote: > On 13.05.21 20:47, Mike Rapoport wrote: > > From: Mike Rapoport > > > > Removing of the pages from the direct map may cause its fragmentation > > on architectures that use large pages to map the physical memory > > which affects the system performance. However, the original Kconfig > > text for CONFIG_DIRECT_GBPAGES said that gigabyte pages in the direct > > map "... can improve the kernel's performance a tiny bit ..." (commit > > 00d1c5e05736 ("x86: add gbpages switches")) and the recent report [1] > > showed that "... although 1G mappings are a good default choice, > > there is no compelling evidence that it must be the only choice". > > Hence, it is sufficient to have secretmem disabled by default with > > the ability of a system administrator to enable it at boot time. > > Maybe add a link to the Intel performance evaluation. " ... the recent report [1]" and the link below. > > Pages in the secretmem regions are unevictable and unmovable to > > avoid accidental exposure of the sensitive data via swap or during > > page migration. ... > > A page that was a part of the secret memory area is cleared when it > > is freed to ensure the data is not exposed to the next user of that > > page. > > You could skip that with init_on_free (and eventually also with > init_on_alloc) set to avoid double clearing. Right, but for now I'd prefer to keep this explicit in the secretmem implementation. We may add the check for init_on_free/init_on_alloc later on. > > [1] > > https://lore.kernel.org/linux-mm/213b4567-46ce-f116-9cdf-bbd0c884eb3c@linux.intel.com/ > -- Sincerely yours, Mike.