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=-5.0 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,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 1FBDEC433EF for ; Fri, 3 Sep 2021 16:11:33 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id A8AB16023B for ; Fri, 3 Sep 2021 16:11:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org A8AB16023B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:38238 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mMBmt-0003im-Sm for qemu-devel@archiver.kernel.org; Fri, 03 Sep 2021 12:11:31 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:59228) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mMBdJ-0004L5-Ds for qemu-devel@nongnu.org; Fri, 03 Sep 2021 12:01:37 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:32750) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mMBdH-0005FH-9u for qemu-devel@nongnu.org; Fri, 03 Sep 2021 12:01:37 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1630684894; 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=ybHw7U4g3iVRZxIp5kFJ8XRmPMWIYv/Oqv8Fl2TUX8o=; b=NYZzEOjlU3Fwxl/z0vi6mpys/wLJ51NjIg8yZzE1/n6egZvdFxF4pnqpOOS9mtvb8qeJA3 Ib4Z2E6GBwokvWo1zR6wIueq+oH7E0/GryK9W3qz9nijIfsg9CZ1KiaRjeubGchnh9I0fS mxsrJINgWC4m1PM9fiL/hahgfiPfa2Q= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-320-gofoRV0fOo-HWvDl8q6ZYg-1; Fri, 03 Sep 2021 12:01:30 -0400 X-MC-Unique: gofoRV0fOo-HWvDl8q6ZYg-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A7D01DF8A5; Fri, 3 Sep 2021 16:01:28 +0000 (UTC) Received: from redhat.com (unknown [10.39.193.241]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 52B7D19C59; Fri, 3 Sep 2021 16:01:21 +0000 (UTC) Date: Fri, 3 Sep 2021 17:01:18 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Markus Armbruster Subject: Re: [RFC PATCH v2 12/12] i386/sev: update query-sev QAPI format to handle SEV-SNP Message-ID: References: <20210826222627.3556-1-michael.roth@amd.com> <20210826222627.3556-13-michael.roth@amd.com> <87tuj4qt71.fsf@dusky.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <87tuj4qt71.fsf@dusky.pond.sub.org> User-Agent: Mutt/2.0.7 (2021-05-04) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.392, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Tom Lendacky , Brijesh Singh , Eduardo Habkost , kvm@vger.kernel.org, "Michael S . Tsirkin" , Connor Kuehl , Michael Roth , James Bottomley , qemu-devel@nongnu.org, Eric Blake , "Dr . David Alan Gilbert" , Dov Murik , Paolo Bonzini , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , David Gibson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Sep 01, 2021 at 04:14:10PM +0200, Markus Armbruster wrote: > Michael Roth writes: > > > Most of the current 'query-sev' command is relevant to both legacy > > SEV/SEV-ES guests and SEV-SNP guests, with 2 exceptions: > > > > - 'policy' is a 64-bit field for SEV-SNP, not 32-bit, and > > the meaning of the bit positions has changed > > - 'handle' is not relevant to SEV-SNP > > > > To address this, this patch adds a new 'sev-type' field that can be > > used as a discriminator to select between SEV and SEV-SNP-specific > > fields/formats without breaking compatibility for existing management > > tools (so long as management tools that add support for launching > > SEV-SNP guest update their handling of query-sev appropriately). > > Technically a compatibility break: query-sev can now return an object > that whose member @policy has different meaning, and also lacks @handle. > > Matrix: > > Old mgmt app New mgmt app > Old QEMU, SEV/SEV-ES good good(1) > New QEMU, SEV/SEV-ES good(2) good > New QEMU, SEV-SNP bad(3) good > > Notes: > > (1) As long as the management application can cope with absent member > @sev-type. > > (2) As long as the management application ignores unknown member > @sev-type. > > (3) Management application may choke on missing member @handle, or > worse, misinterpret member @policy. Can only happen when something > other than the management application created the SEV-SNP guest (or the > user somehow made the management application create one even though it > doesn't know how, say with CLI option passthrough, but that's always > fragile, and I wouldn't worry about it here). > > I think (1) and (2) are reasonable. (3) is an issue for management > applications that support attaching to existing guests. Thoughts? IIUC you can only reach scenario (3) if you have created a guest using '-object sev-snp-guest', which is a new feature introduced in patch 2. IOW, scenario (3) old mgmt app + new QEMU + sev-snp guest does not exist as a combination. Thus the (bad) field is actually (n/a) So I believe this proposed change is acceptable in all scenarios with existing deployed usage, as well as all newly introduced scenarios. 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 :|