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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4B546C001DE for ; Mon, 31 Jul 2023 16:52:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233552AbjGaQw0 (ORCPT ); Mon, 31 Jul 2023 12:52:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51274 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229998AbjGaQwY (ORCPT ); Mon, 31 Jul 2023 12:52:24 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0B0461728 for ; Mon, 31 Jul 2023 09:51:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1690822297; h=from:from:reply-to:reply-to:subject:subject: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=JvLXCcMmGv5hKdcLx3cUZEwjA2OrWpQwWaxNmIEK5uM=; b=VW08Inc12NKBgAY0LFEg4I0s2ZMV9Xm3nPBw8aJbvSfY5Xi9BCJsGyTbpNbm2UqBEemgyB VCw958mTws/pdBaGySVF/9hAnZoZWklsI7PLu8UekH0mJC+DiIcVZo+a/GM5Ke3SmUsJng ne+rvfO14VXZRNBPeDbDycaaKfIrZj4= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-679-R0vH1opIM9S4G6o22AH58g-1; Mon, 31 Jul 2023 12:51:34 -0400 X-MC-Unique: R0vH1opIM9S4G6o22AH58g-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 64C5F894EDC; Mon, 31 Jul 2023 16:51:33 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.93]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 261BB1121325; Mon, 31 Jul 2023 16:51:31 +0000 (UTC) Date: Mon, 31 Jul 2023 17:51:28 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Xiaoyao Li Cc: Paolo Bonzini , Sean Christopherson , David Hildenbrand , Igor Mammedov , "Michael S. Tsirkin" , Marcel Apfelbaum , Richard Henderson , Marcelo Tosatti , Markus Armbruster , Eric Blake , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Peter Xu , Chao Peng , Michael Roth , isaku.yamahata@gmail.com, qemu-devel@nongnu.org, kvm@vger.kernel.org Subject: Re: [RFC PATCH 00/19] QEMU gmem implemention Message-ID: Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <20230731162201.271114-1-xiaoyao.li@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20230731162201.271114-1-xiaoyao.li@intel.com> User-Agent: Mutt/2.2.9 (2022-11-12) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, Jul 31, 2023 at 12:21:42PM -0400, Xiaoyao Li wrote: > This is the first RFC version of enabling KVM gmem[1] as the backend for > private memory of KVM_X86_PROTECTED_VM. > > It adds the support to create a specific KVM_X86_PROTECTED_VM type VM, > and introduces 'private' property for memory backend. When the vm type > is KVM_X86_PROTECTED_VM and memory backend has private enabled as below, > it will call KVM gmem ioctl to allocate private memory for the backend. > > $qemu -object memory-backend-ram,id=mem0,size=1G,private=on \ > -machine q35,kvm-type=sw-protected-vm,memory-backend=mem0 \ > ... > > Unfortunately this patch series fails the boot of OVMF at very early > stage due to triple fault because KVM doesn't support emulate string IO > to private memory. We leave it as an open to be discussed. > > There are following design opens that need to be discussed: > > 1. how to determine the vm type? > > a. like this series, specify the vm type via machine property > 'kvm-type' > b. check the memory backend, if any backend has 'private' property > set, the vm-type is set to KVM_X86_PROTECTED_VM. > > 2. whether 'private' property is needed if we choose 1.b as design > > with 1.b, QEMU can decide whether the memory region needs to be > private (allocates gmem fd for it) or not, on its own. > > 3. What is KVM_X86_SW_PROTECTED_VM going to look like? What's the > purose of it and what's the requirement on it. I think it's the > questions for KVM folks than QEMU folks. > > Any other idea/open/question is welcomed. > > > Beside, TDX QEMU implemetation is based on this series to provide > private gmem for TD private memory, which can be found at [2]. > And it can work corresponding KVM [3] to boot TDX guest. We already have a general purpose configuration mechanism for confidential guests. The -machine argument has a property confidential-guest-support=$OBJECT-ID, for pointing to an object that implements the TYPE_CONFIDENTIAL_GUEST_SUPPORT interface in QEMU. This is implemented with SEV, PPC PEF mode, and s390 protvirt. I would expect TDX to follow this same design ie qemu-system-x86_64 \ -object tdx-guest,id=tdx0,..... \ -machine q35,confidential-guest-support=tdx0 \ ... and not require inventing the new 'kvm-type' attribute at least. For the memory backend though, I'm not so sure - possibly that might be something that still wants an extra property to identify the type of memory to allocate, since we use memory-backend-ram for a variety of use cases. Or it could be an entirely new object type such as "memory-backend-gmem" With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|