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[142.162.113.129]) by smtp.gmail.com with ESMTPSA id s13sm4716120qki.23.2021.11.22.06.01.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Nov 2021 06:01:49 -0800 (PST) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1mp9tE-00DsN8-Ie; Mon, 22 Nov 2021 10:01:48 -0400 Date: Mon, 22 Nov 2021 10:01:48 -0400 From: Jason Gunthorpe To: David Hildenbrand Cc: Chao Peng , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, qemu-devel@nongnu.org, Paolo Bonzini , Jonathan Corbet , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H . Peter Anvin" , Hugh Dickins , Jeff Layton , "J . Bruce Fields" , Andrew Morton , Yu Zhang , "Kirill A . Shutemov" , luto@kernel.org, john.ji@intel.com, susie.li@intel.com, jun.nakajima@intel.com, dave.hansen@intel.com, ak@linux.intel.com Subject: Re: [RFC v2 PATCH 01/13] mm/shmem: Introduce F_SEAL_GUEST Message-ID: <20211122140148.GR876299@ziepe.ca> References: <20211119134739.20218-1-chao.p.peng@linux.intel.com> <20211119134739.20218-2-chao.p.peng@linux.intel.com> <20211119151943.GH876299@ziepe.ca> <20211119160023.GI876299@ziepe.ca> <4efdccac-245f-eb1f-5b7f-c1044ff0103d@redhat.com> <20211122133145.GQ876299@ziepe.ca> <56c0dffc-5fc4-c337-3e85-a5c9ce619140@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56c0dffc-5fc4-c337-3e85-a5c9ce619140@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 22, 2021 at 02:35:49PM +0100, David Hildenbrand wrote: > On 22.11.21 14:31, Jason Gunthorpe wrote: > > On Mon, Nov 22, 2021 at 10:26:12AM +0100, David Hildenbrand wrote: > > > >> I do wonder if we want to support sharing such memfds between processes > >> in all cases ... we most certainly don't want to be able to share > >> encrypted memory between VMs (I heard that the kernel has to forbid > >> that). It would make sense in the use case you describe, though. > > > > If there is a F_SEAL_XX that blocks every kind of new access, who > > cares if userspace passes the FD around or not? > I was imagining that you actually would want to do some kind of "change > ownership". But yeah, the intended semantics and all use cases we have > in mind are not fully clear to me yet. If it's really "no new access" > (side note: is "access" the right word?) then sure, we can pass the fd > around. What is "ownership" in a world with kvm and iommu are reading pages out of the same fd? "no new access" makes sense to me, we have access through read/write/mmap/splice/etc and access to pages through the private in kernel interface (kvm, iommu) Jason 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 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B1C3FC433EF for ; Mon, 22 Nov 2021 14:05:52 +0000 (UTC) Received: from localhost ([::1]:43900 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mp9x9-0004Ft-MI for qemu-devel@archiver.kernel.org; Mon, 22 Nov 2021 09:05:51 -0500 Received: from eggs.gnu.org ([209.51.188.92]:45146) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mp9tJ-0000V8-UM for qemu-devel@nongnu.org; Mon, 22 Nov 2021 09:01:54 -0500 Received: from [2607:f8b0:4864:20::733] (port=42920 helo=mail-qk1-x733.google.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1mp9tH-00069s-U3 for qemu-devel@nongnu.org; Mon, 22 Nov 2021 09:01:53 -0500 Received: by mail-qk1-x733.google.com with SMTP id g28so18138190qkk.9 for ; Mon, 22 Nov 2021 06:01:50 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=AkVa9dgYFMW65oNWi3lEAnC5wvNaUzrKbDuhcPjVyAM=; b=YbZPXtBUsIP409q2mT8lSr4BqkVNQQ7uwSh3flKk8k1tLdFvFH+qBcjZfbEQuRnSJt ym7KIc8Rr2qe7cnTl58XYSE6lugUqTMCIbLTauRHYkZqs9rs3GKm1bMlBUWI+TRMcDGX I0UZlTo4cd8ySiP1lEYqugVzwPTPEfPtKNmmPzejl2rh3HDr1pH7Jp2W80NczxtpUT2f 7DZmFWyXm06nxDnZOIMEP5lLL2tkQARwppJwaeUpCzINEB5Wi61hhIuu1iPds6HyRHDs CkaIWL9eMwFvW3dqc9J2iSLvyxaUEjT+FHbVEY0VTDVLySkuR3731mB61RPDNMhCVl2Y 9yWg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=AkVa9dgYFMW65oNWi3lEAnC5wvNaUzrKbDuhcPjVyAM=; b=ToFSez9Aj6eDjygUUodquiPmldcjWe8BAGRpWQihiInNuEMHUYV/8DFlpY0b2pSPNA 5BMsAFCAtsNZYPHHqoKYdwcpPyjl+kfMmhbq77lDH/UkU2sKIUTPvQS87I7jTXQYkcMx iyL94KN/a3hfVh8eCYlUa4/74hSVaxcM0YBrznea5O29k19zKaWYJ3NC1oexLIJeMKuS v5JNLrC4gEAsf9CZJJN4qwitBYhO79hIeFeYlwkMvWu+b2zfrAYCCR3ydigAxO1Iijnz 3Pm2yc5w/qf5sC9K07ohmUE8KI/dTS6RSUU32P4psucQET2OLI5Wy/kq32tU00KChyRo OJeQ== X-Gm-Message-State: AOAM530zO8jsgx7N7gs1se1yVm92kmkHFUhGQasjH4RD56Mu7DAPqezr pFM6b5G4MAGAVKZba2uubgXj/Q== X-Google-Smtp-Source: ABdhPJx4FBEsFukDClDSwGw8qd9OgvbrBef1ytO7EqEtX4yVEQkSoyHCZqYrRFEAi40duExffLYOuw== X-Received: by 2002:a05:620a:190b:: with SMTP id bj11mr47809423qkb.514.1637589709646; Mon, 22 Nov 2021 06:01:49 -0800 (PST) Received: from ziepe.ca (hlfxns017vw-142-162-113-129.dhcp-dynamic.fibreop.ns.bellaliant.net. [142.162.113.129]) by smtp.gmail.com with ESMTPSA id s13sm4716120qki.23.2021.11.22.06.01.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Nov 2021 06:01:49 -0800 (PST) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1mp9tE-00DsN8-Ie; Mon, 22 Nov 2021 10:01:48 -0400 Date: Mon, 22 Nov 2021 10:01:48 -0400 From: Jason Gunthorpe To: David Hildenbrand Subject: Re: [RFC v2 PATCH 01/13] mm/shmem: Introduce F_SEAL_GUEST Message-ID: <20211122140148.GR876299@ziepe.ca> References: <20211119134739.20218-1-chao.p.peng@linux.intel.com> <20211119134739.20218-2-chao.p.peng@linux.intel.com> <20211119151943.GH876299@ziepe.ca> <20211119160023.GI876299@ziepe.ca> <4efdccac-245f-eb1f-5b7f-c1044ff0103d@redhat.com> <20211122133145.GQ876299@ziepe.ca> <56c0dffc-5fc4-c337-3e85-a5c9ce619140@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56c0dffc-5fc4-c337-3e85-a5c9ce619140@redhat.com> X-Host-Lookup-Failed: Reverse DNS lookup failed for 2607:f8b0:4864:20::733 (failed) Received-SPF: pass client-ip=2607:f8b0:4864:20::733; envelope-from=jgg@ziepe.ca; helo=mail-qk1-x733.google.com X-Spam_score_int: -12 X-Spam_score: -1.3 X-Spam_bar: - X-Spam_report: (-1.3 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, PDS_HP_HELO_NORDNS=0.001, RCVD_IN_DNSWL_NONE=-0.0001, RDNS_NONE=0.793, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Wanpeng Li , jun.nakajima@intel.com, kvm@vger.kernel.org, qemu-devel@nongnu.org, "J . Bruce Fields" , linux-mm@kvack.org, "H . Peter Anvin" , Chao Peng , ak@linux.intel.com, Jonathan Corbet , Joerg Roedel , x86@kernel.org, Hugh Dickins , Ingo Molnar , Borislav Petkov , luto@kernel.org, Thomas Gleixner , Vitaly Kuznetsov , Jim Mattson , dave.hansen@intel.com, Sean Christopherson , susie.li@intel.com, Jeff Layton , linux-kernel@vger.kernel.org, john.ji@intel.com, Yu Zhang , linux-fsdevel@vger.kernel.org, Paolo Bonzini , Andrew Morton , "Kirill A . Shutemov" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, Nov 22, 2021 at 02:35:49PM +0100, David Hildenbrand wrote: > On 22.11.21 14:31, Jason Gunthorpe wrote: > > On Mon, Nov 22, 2021 at 10:26:12AM +0100, David Hildenbrand wrote: > > > >> I do wonder if we want to support sharing such memfds between processes > >> in all cases ... we most certainly don't want to be able to share > >> encrypted memory between VMs (I heard that the kernel has to forbid > >> that). It would make sense in the use case you describe, though. > > > > If there is a F_SEAL_XX that blocks every kind of new access, who > > cares if userspace passes the FD around or not? > I was imagining that you actually would want to do some kind of "change > ownership". But yeah, the intended semantics and all use cases we have > in mind are not fully clear to me yet. If it's really "no new access" > (side note: is "access" the right word?) then sure, we can pass the fd > around. What is "ownership" in a world with kvm and iommu are reading pages out of the same fd? "no new access" makes sense to me, we have access through read/write/mmap/splice/etc and access to pages through the private in kernel interface (kvm, iommu) Jason