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 6AB4DC00140 for ; Sun, 21 Aug 2022 10:42:12 +0000 (UTC) Received: from localhost ([::1]:56816 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oPiPC-0006tL-Jj for qemu-devel@archiver.kernel.org; Sun, 21 Aug 2022 06:42:11 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:39478) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oPiBl-0004km-Fz for qemu-devel@nongnu.org; Sun, 21 Aug 2022 06:28:20 -0400 Received: from casper.infradead.org ([2001:8b0:10b:1236::1]:50470) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oPiBj-0004Lk-1M for qemu-devel@nongnu.org; Sun, 21 Aug 2022 06:28:17 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=ezqnpfSoqTQDMJ+hJHVpOcv6CdCxoRGL+MI+YKi2ajc=; b=oGft0gECLBoMj2UBuNjBRRw7oU +dq00PAmbDXUBvlm8/tj+3wvQ6+u1mI4tCmpI7ekjaZJY5bZRNO9OebH9SJpV1ysh/OWtfztRfWPW oh7BrM3UcOp9ibf9eSMPU5DoNPWCirAlzoF7UBdHCRQtmm6dE/aZytFO5kBG+bAYbqLdyYZzrVtt/ iuZP3zYaHC4+P7CXpDkHhx26k0MpnTHE/dEowsrIT+sGbKv23kjGfdNLUtoruLSmY1Y3DtZhd/9Hl 3LYOd+8SlRhwWalnWFB/NWtwuYs86Tc9tyA9RmJoFdeb0dwyoEDgnWuoUSo1B+PY04MuuTWMM54Av EsSC0QFw==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1oPiBE-00D7rG-Sc; Sun, 21 Aug 2022 10:27:44 +0000 Date: Sun, 21 Aug 2022 11:27:44 +0100 From: Matthew Wilcox To: Hugh Dickins Cc: "Kirill A . Shutemov" , Chao Peng , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, linux-doc@vger.kernel.org, qemu-devel@nongnu.org, linux-kselftest@vger.kernel.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" , Jeff Layton , "J . Bruce Fields" , Andrew Morton , Shuah Khan , Mike Rapoport , Steven Price , "Maciej S . Szmigiero" , Vlastimil Babka , Vishal Annapurve , Yu Zhang , luto@kernel.org, jun.nakajima@intel.com, dave.hansen@intel.com, ak@linux.intel.com, david@redhat.com, aarcange@redhat.com, ddutile@redhat.com, dhildenb@redhat.com, Quentin Perret , Michael Roth , mhocko@suse.com, Muchun Song , "Gupta, Pankaj" Subject: Re: [PATCH v7 00/14] KVM: mm: fd-based approach for supporting KVM guest private memory Message-ID: References: <20220706082016.2603916-1-chao.p.peng@linux.intel.com> <20220818132421.6xmjqduempmxnnu2@box> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Received-SPF: none client-ip=2001:8b0:10b:1236::1; envelope-from=willy@infradead.org; helo=casper.infradead.org X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 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, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_NONE=0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Aug 18, 2022 at 08:00:41PM -0700, Hugh Dickins wrote: > tmpfs and hugetlbfs and page cache are designed around sharing memory: > TDX is designed around absolutely not sharing memory; and the further > uses which Sean foresees appear not to need it as page cache either. > > Except perhaps for page migration reasons. It's somewhat incidental, > but of course page migration knows how to migrate page cache, so > masquerading as page cache will give a short cut to page migration, > when page migration becomes at all possible. I haven't read the patch series, and I'm not taking a position one way or the other on whether this is better implemented as a shmem addition or a shim that asks shmem for memory. Page migration can be done for driver memory by using PageMovable. I just rewrote how it works, so the details are top of my mind at the moment if anyone wants something explained. Commit 68f2736a8583 is the key one to look at.