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 CE07AC433EF for ; Fri, 3 Sep 2021 16:10:38 +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 388E0610CF for ; Fri, 3 Sep 2021 16:10:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 388E0610CF 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]:35262 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mMBm1-0001ah-55 for qemu-devel@archiver.kernel.org; Fri, 03 Sep 2021 12:10:37 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:58708) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mMBaV-0000Ko-19 for qemu-devel@nongnu.org; Fri, 03 Sep 2021 11:58:43 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:38000) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mMBaT-0002tW-0G for qemu-devel@nongnu.org; Fri, 03 Sep 2021 11:58:42 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1630684720; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=AotTT4cFDUcxarYUeWBvMDYMrkfWVw5v2aHjM+zv9gE=; b=Etc1VnVZejCzgTzL1D6ab6sMxFXMpV8MuMJ5HxiTvvozLLgF1RvwDfWGiC8SEJreDofNJR R2fGIrqOkdpkvXgs1aLHfpxPjvOH1D3kAd5ZzpToBQqWjaGR+PAN2r3qMZz9s7ofSPKCtZ ZEZbfPuf4bBVyBa9To5nqFH8haeei7A= 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-279-xeEMUaq1OEC0G4Dj7tGyXw-1; Fri, 03 Sep 2021 11:58:39 -0400 X-MC-Unique: xeEMUaq1OEC0G4Dj7tGyXw-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9155884A5ED; Fri, 3 Sep 2021 15:58:37 +0000 (UTC) Received: from redhat.com (unknown [10.39.193.241]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8A58460BF1; Fri, 3 Sep 2021 15:58:08 +0000 (UTC) Date: Fri, 3 Sep 2021 16:58:05 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Michael Roth 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> <20210903151316.zveiegbo42o2gttq@amd.com> <20210903154319.zxvgccxayjoabtck@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20210903154319.zxvgccxayjoabtck@amd.com> User-Agent: Mutt/2.0.7 (2021-05-04) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Received-SPF: pass client-ip=216.205.24.124; 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 , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , James Bottomley , Markus Armbruster , qemu-devel@nongnu.org, Dov Murik , Paolo Bonzini , Eric Blake , "Dr . David Alan Gilbert" , David Gibson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, Sep 03, 2021 at 10:43:19AM -0500, Michael Roth wrote: > On Fri, Sep 03, 2021 at 04:30:48PM +0100, Daniel P. Berrangé wrote: > > On Fri, Sep 03, 2021 at 10:13:16AM -0500, Michael Roth wrote: > > > 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? > > > > > > Hmm... yah I hadn't considering 'old mgmt' trying to interact with a SNP > > > guest started through some other means. > > > > > > Don't really see an alternative other than introducing a new > > > 'query-sev-snp', but that would still leave 'old mgmt' broken, since > > > it might still call do weird stuff like try to interpret the SNP policy > > > as an SEV/SEV-ES and end up with some very unexpected results. So if I > > > did go this route, I would need to have QMP begin returning an error if > > > query-sev is run against an SNP guest. But currently for non-SEV guests > > > it already does: > > > > > > error_setg(errp, "SEV feature is not available") > > > > > > so 'old mgmt' should be able to handle the error just fine. > > > > > > Would that approach be reasonable? > > > > This ties into the question I've just sent in my other mail. > > > > If the hardware strictly requires that guest are created in SEV-SNP > > mode only, and will not support SEV/SEV-ES mode, then we need to > > ensure "query-sev" reports the feature as not-available, so that > > existing mgmt apps don't try to use SEV/SEV-ES. > > An SEV-SNP-capable host can run both 'legacy' SEV/SEV-ES, as well as > SEV-SNP guests, at the same time. But as far as QEMU goes, we need > to specify one or the other explicitly at launch time, via existing > 'sev-guest', or the new 'sev-snp-guest' ConfidentialGuestSupport type. > > > > > If the SEV-SNP hardware is functionally back-compatible with a gues > > configured in SEV/SEV-ES mode, then we souldn't need a new command, > > just augment th eexisting command with additional field(s), to > > indicate existance of SEV-SNP features. > > query-sev-info provides information specific to the guest instance, > like the configured policy. Are you thinking of query-sev-capabilities, > which reports some host-wide information and should indeed remain > available for either case. (and maybe should also be updated to report > on SEV-SNP availability for the host?) Oh right, yes, I am getting confused with query-sev-capabilities. I think this means everything is OK with your query-sev-info changes proposed here, I'll reply direct to Markus' point though. 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 :|