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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 762C6C43214 for ; Wed, 1 Sep 2021 10:24:54 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0AD1061057 for ; Wed, 1 Sep 2021 10:24:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 0AD1061057 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 61EDB6B006C; Wed, 1 Sep 2021 06:24:53 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5A8286B0071; Wed, 1 Sep 2021 06:24:53 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 46F4F6B0072; Wed, 1 Sep 2021 06:24:53 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0218.hostedemail.com [216.40.44.218]) by kanga.kvack.org (Postfix) with ESMTP id 33D0A6B006C for ; Wed, 1 Sep 2021 06:24:53 -0400 (EDT) Received: from smtpin37.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id E43E9181D75D6 for ; Wed, 1 Sep 2021 10:24:52 +0000 (UTC) X-FDA: 78538621224.37.E58DA2C Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by imf03.hostedemail.com (Postfix) with ESMTP id 26C3B30000A5 for ; Wed, 1 Sep 2021 10:24:51 +0000 (UTC) X-IronPort-AV: E=McAfee;i="6200,9189,10093"; a="240978690" X-IronPort-AV: E=Sophos;i="5.84,369,1620716400"; d="scan'208";a="240978690" Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Sep 2021 03:24:50 -0700 X-IronPort-AV: E=Sophos;i="5.84,369,1620716400"; d="scan'208";a="645686130" Received: from zhibosun-mobl2.ccr.corp.intel.com (HELO localhost) ([10.255.31.93]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Sep 2021 03:24:40 -0700 Date: Wed, 1 Sep 2021 18:24:37 +0800 From: Yu Zhang To: Andy Lutomirski Cc: David Hildenbrand , Sean Christopherson , Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm list , Linux Kernel Mailing List , Borislav Petkov , Andrew Morton , Joerg Roedel , Andi Kleen , David Rientjes , Vlastimil Babka , Tom Lendacky , Thomas Gleixner , "Peter Zijlstra (Intel)" , Ingo Molnar , Varad Gautam , Dario Faggioli , the arch/x86 maintainers , linux-mm@kvack.org, linux-coco@lists.linux.dev, "Kirill A. Shutemov" , "Kirill A . Shutemov" , Sathyanarayanan Kuppuswamy , Dave Hansen Subject: Re: [RFC] KVM: mm: fd-based approach for supporting KVM guest private memory Message-ID: <20210901102437.g5wrgezmrjqn3mvy@linux.intel.com> References: <20210824005248.200037-1-seanjc@google.com> <307d385a-a263-276f-28eb-4bc8dd287e32@redhat.com> <20210827023150.jotwvom7mlsawjh4@linux.intel.com> <8f3630ff-bd6d-4d57-8c67-6637ea2c9560@www.fastmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8f3630ff-bd6d-4d57-8c67-6637ea2c9560@www.fastmail.com> User-Agent: NeoMutt/20171215 Authentication-Results: imf03.hostedemail.com; dkim=none; spf=none (imf03.hostedemail.com: domain of yu.c.zhang@linux.intel.com has no SPF policy when checking 192.55.52.88) smtp.mailfrom=yu.c.zhang@linux.intel.com; dmarc=fail reason="No valid SPF, No valid DKIM" header.from=intel.com (policy=none) X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 26C3B30000A5 X-Stat-Signature: ek8fbpzd9u8udqfrst85rzjktgqrcjpo X-HE-Tag: 1630491891-955137 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Aug 31, 2021 at 09:53:27PM -0700, Andy Lutomirski wrote: > > > On Thu, Aug 26, 2021, at 7:31 PM, Yu Zhang wrote: > > On Thu, Aug 26, 2021 at 12:15:48PM +0200, David Hildenbrand wrote: > > > Thanks a lot for this summary. A question about the requirement: do we or > > do we not have plan to support assigned device to the protected VM? > > > > If yes. The fd based solution may need change the VFIO interface as well( > > though the fake swap entry solution need mess with VFIO too). Because: > > > > 1> KVM uses VFIO when assigning devices into a VM. > > > > 2> Not knowing which GPA ranges may be used by the VM as DMA buffer, all > > guest pages will have to be mapped in host IOMMU page table to host pages, > > which are pinned during the whole life cycle fo the VM. > > > > 3> IOMMU mapping is done during VM creation time by VFIO and IOMMU driver, > > in vfio_dma_do_map(). > > > > 4> However, vfio_dma_do_map() needs the HVA to perform a GUP to get the HPA > > and pin the page. > > > > But if we are using fd based solution, not every GPA can have a HVA, thus > > the current VFIO interface to map and pin the GPA(IOVA) wont work. And I > > doubt if VFIO can be modified to support this easily. > > > > > > Do you mean assigning a normal device to a protected VM or a hypothetical protected-MMIO device? > > If the former, it should work more or less like with a non-protected VM. mmap the VFIO device, set up a memslot, and use it. I'm not sure whether anyone will actually do this, but it should be possible, at least in principle. Maybe someone will want to assign a NIC to a TDX guest. An NVMe device with the understanding that the guest can't trust it wouldn't be entirely crazy ether. > > If the latter, AFAIK there is no spec for how it would work even in principle. Presumably it wouldn't work quite like VFIO -- instead, the kernel could have a protection-virtual-io-fd mechanism, and that fd could be bound to a memslot in whatever way we settle on for binding secure memory to a memslot. > Thanks Andy. I was asking the first scenario. Well, I agree it is doable if someone really want some assigned device in TD guest. As Kevin mentioned in his reply, HPA can be generated, by extending VFIO with a new mapping protocol which uses fd+offset, instead of HVA. Another issue is current TDX does not support DMA encryption, and only shared GPA memory shall be mapped in the VT-d. So to support this, KVM may need to work with VFIO to dynamically program host IOPT(IOMMU Page Table) when TD guest notifies a shared GFN range(e.g., with a MAP_GPA TDVMCALL), instead of prepopulating the IOPT at VM creation time, by mapping entire GFN ranges of a guest. So my inclination would be to just disallow using of VFIO device in TDX first, until we have real requirement(with above enabling work finished). B.R. Yu