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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 515E6C433F5 for ; Wed, 6 Apr 2022 18:43:06 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9F5316B0071; Wed, 6 Apr 2022 14:42:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9A45B6B0073; Wed, 6 Apr 2022 14:42:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 81DC06B0074; Wed, 6 Apr 2022 14:42:55 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.26]) by kanga.kvack.org (Postfix) with ESMTP id 70BC56B0071 for ; Wed, 6 Apr 2022 14:42:55 -0400 (EDT) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 2D77424B53 for ; Wed, 6 Apr 2022 18:42:45 +0000 (UTC) X-FDA: 79327325490.02.EF3348A Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf21.hostedemail.com (Postfix) with ESMTP id 6B61E1C0022 for ; Wed, 6 Apr 2022 18:42:44 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 6B4EA61CAF; Wed, 6 Apr 2022 18:42:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 30FAFC385A6; Wed, 6 Apr 2022 18:42:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1649270562; bh=sbHbRXEyEAYhEDFwzan7utBqpNK0sjzefEArFgF8uSU=; h=In-Reply-To:References:Date:From:To:Cc:Subject:From; b=eIaWhMw6qdMVoRFxQeR1SfjCYwZy9RX4+1QgPmQTaYkMgXq5EQ0sAVb/ULadR9MI7 LH+S/c+4WuHCz9BUADIJglVSfcRcc6WejwYyM8Zb7kxiMxjNjlQQDilGIN/w8F20LF hrAlrpaJiEnF7GwrtgY3GeH3IG43iicZf7iLsWrBPdjz0Xcg62zOdFu6x9zo7xgJk5 hq2ap75faI5QFkM7ufk+5PP4JDHKHirOI6tOCxRHtxkvbVauUHCe7lAi4Fdoyzj8y9 G3ucqOIFtsChrg/dqSy9ybRF2yetOLigWYzb0CjPhvgDFTZx/nxy8vUOVNf/cZzrqO oArXJrEdmbMlg== Received: from compute2.internal (compute2.nyi.internal [10.202.2.46]) by mailauth.nyi.internal (Postfix) with ESMTP id 0C18527C005B; Wed, 6 Apr 2022 14:42:39 -0400 (EDT) Received: from imap48 ([10.202.2.98]) by compute2.internal (MEProxy); Wed, 06 Apr 2022 14:42:40 -0400 X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvvddrudejiedguddvkecutefuodetggdotefrod ftvfcurfhrohhfihhlvgemucfhrghsthforghilhdpqfgfvfdpuffrtefokffrpgfnqfgh necuuegrihhlohhuthemuceftddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmd enucfjughrpefofgggkfgjfhffhffvufgtsehttdertderredtnecuhfhrohhmpedftehn ugihucfnuhhtohhmihhrshhkihdfuceolhhuthhosehkvghrnhgvlhdrohhrgheqnecugg ftrfgrthhtvghrnheptdfhheettddvtedvtedugfeuuefhtddugedvleevleefvdetleff gfefvdekgeefnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehmrghilhhfrh homheprghnugihodhmvghsmhhtphgruhhthhhpvghrshhonhgrlhhithihqdduudeiudek heeifedvqddvieefudeiiedtkedqlhhuthhopeepkhgvrhhnvghlrdhorhhgsehlihhnuh igrdhluhhtohdruhhs X-ME-Proxy: Received: by mailuser.nyi.internal (Postfix, from userid 501) id 8341B21E006E; Wed, 6 Apr 2022 14:42:38 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface User-Agent: Cyrus-JMAP/3.7.0-alpha0-385-g3a17909f9e-fm-20220404.001-g3a17909f Mime-Version: 1.0 Message-Id: <4ae11ddc-0fe6-4644-a30e-006d99dba456@www.fastmail.com> In-Reply-To: References: <80aad2f9-9612-4e87-a27a-755d3fa97c92@www.fastmail.com> <83fd55f8-cd42-4588-9bf6-199cbce70f33@www.fastmail.com> <54acbba9-f4fd-48c1-9028-d596d9f63069@www.fastmail.com> Date: Wed, 06 Apr 2022 11:42:17 -0700 From: "Andy Lutomirski" To: "Sean Christopherson" Cc: "Quentin Perret" , "Steven Price" , "Chao Peng" , "kvm list" , "Linux Kernel Mailing List" , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, "Linux API" , qemu-devel@nongnu.org, "Paolo Bonzini" , "Jonathan Corbet" , "Vitaly Kuznetsov" , "Wanpeng Li" , "Jim Mattson" , "Joerg Roedel" , "Thomas Gleixner" , "Ingo Molnar" , "Borislav Petkov" , "the arch/x86 maintainers" , "H. Peter Anvin" , "Hugh Dickins" , "Jeff Layton" , "J . Bruce Fields" , "Andrew Morton" , "Mike Rapoport" , "Maciej S . Szmigiero" , "Vlastimil Babka" , "Vishal Annapurve" , "Yu Zhang" , "Kirill A. Shutemov" , "Nakajima, Jun" , "Dave Hansen" , "Andi Kleen" , "David Hildenbrand" , "Marc Zyngier" , "Will Deacon" Subject: Re: [PATCH v5 00/13] KVM: mm: fd-based approach for supporting KVM guest private memory Content-Type: text/plain X-Stat-Signature: gsmw45kzyfudimcaz6w9s4b49e43ukj1 Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=eIaWhMw6; spf=pass (imf21.hostedemail.com: domain of luto@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=luto@kernel.org; dmarc=pass (policy=none) header.from=kernel.org X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 6B61E1C0022 X-HE-Tag: 1649270564-147144 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, Apr 5, 2022, at 11:30 AM, Sean Christopherson wrote: > On Tue, Apr 05, 2022, Andy Lutomirski wrote: > >> resume guest >> *** host -> hypervisor -> guest *** >> Guest unshares the page. >> *** guest -> hypervisor *** >> Hypervisor removes PTE. TLBI. >> *** hypervisor -> guest *** >> >> Obviously considerable cleverness is needed to make a virt IOMMU like this >> work well, but still. >> >> Anyway, my suggestion is that the fd backing proposal get slightly modified >> to get it ready for multiple subtypes of backing object, which should be a >> pretty minimal change. Then, if someone actually needs any of this >> cleverness, it can be added later. In the mean time, the >> pread()/pwrite()/splice() scheme is pretty good. > > Tangentially related to getting private-fd ready for multiple things, > what about > implementing the pread()/pwrite()/splice() scheme in pKVM itself? I.e. > read() on > the VM fd, with the offset corresponding to gfn in some way. > Hmm, could make sense.