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 8E0D8C433DB for ; Tue, 16 Feb 2021 16:53:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5C2EC64DCF for ; Tue, 16 Feb 2021 16:53:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229784AbhBPQw0 (ORCPT ); Tue, 16 Feb 2021 11:52:26 -0500 Received: from mx2.suse.de ([195.135.220.15]:56872 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229699AbhBPQwX (ORCPT ); Tue, 16 Feb 2021 11:52:23 -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=1613494295; 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=fv1cqvwsI0OzZQzjo9Fzqiw9J9sAKYM15trtTiADU8I=; b=m+7A3yBnlzXwcSFUtKDR2Y9JcLQQ7GBKZLbjSDY4uRJe8Oprcc1t3A0Yb4nCpmSjJzTq71 m2lvwh4POgKc94rijkZTo8EsctDQ8udo5YFmIVVBqcDZmQE+zdGsrWJMYIvr1Q40Hpav5m AI5AIoiWGkF74EgEjx/NO759Sl7hNIs= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 93467AE05; Tue, 16 Feb 2021 16:51:35 +0000 (UTC) Date: Tue, 16 Feb 2021 17:51:34 +0100 From: Michal Hocko To: James Bottomley Cc: David Hildenbrand , Mike Rapoport , Mike Rapoport , 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 , 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 v17 07/10] mm: introduce memfd_secret system call to create "secret" memory areas Message-ID: References: <20210214091954.GM242749@kernel.org> <052DACE9-986B-424C-AF8E-D6A4277DE635@redhat.com> <244f86cba227fa49ca30cd595c4e5538fe2f7c2b.camel@linux.ibm.com> <12c3890b233c8ec8e3967352001a7b72a8e0bfd0.camel@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <12c3890b233c8ec8e3967352001a7b72a8e0bfd0.camel@linux.ibm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On Tue 16-02-21 08:25:39, James Bottomley wrote: > On Mon, 2021-02-15 at 20:20 +0100, Michal Hocko wrote: > [...] > > > > What kind of flags are we talking about and why would that be a > > > > problem with memfd_create interface? Could you be more specific > > > > please? > > > > > > You mean what were the ioctl flags in the patch series linked > > > above? They were SECRETMEM_EXCLUSIVE and SECRETMEM_UNCACHED in > > > patch 3/5. > > > > OK I see. How many potential modes are we talking about? A few or > > potentially many? > > Well I initially thought there were two (uncached or not) until you > came up with the migratable or non-migratable, which affects the > security properties. But now there's also potential for hardware > backing, like mktme, described by flags as well. I do not remember details about mktme but from what I still recall it had keys associated with direct maps. Is the key management something that fits into flags management? > I suppose you could > also use RDT to restrict which cache the data goes into: say L1 but not > L2 on to lessen the impact of fully uncached (although the big thrust > of uncached was to blunt hyperthread side channels). So there is > potential for quite a large expansion even though I'd be willing to bet > that a lot of the modes people have thought about turn out not to be > very effective in the field. Are those very HW specific features really viable through a generic syscall? Don't get me wrong but I find it much more likely somebody will want a hugetlb (pretty HW independent) without a direct map than a very close to the HW caching mode soon. But thanks for the clarification anyway. -- Michal Hocko SUSE Labs