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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5B1F3C433F5 for ; Tue, 16 Nov 2021 17:23:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 388FD619E1 for ; Tue, 16 Nov 2021 17:23:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238576AbhKPR0z (ORCPT ); Tue, 16 Nov 2021 12:26:55 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:31233 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235906AbhKPR0z (ORCPT ); Tue, 16 Nov 2021 12:26:55 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1637083437; 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=2NZ/bQb6pXmOARjezvrKo/KDHB+GdPermNVE2URZCtA=; b=NQOhyuwPors7cZ6ZJU3801WoZ0Rn2h/Sr31I4BzhKkjnpthc5dIMutbDMF3UHQtldQm13U Sq+KEeSCcr1dMCHZbuodn70f2/M+JlMijvhizCfGE247JEDAeB2vaT4Orku98Oqt2FSNdk 3TsOuzfC1c8KN6OU7faRs1X9kbIEQ3A= 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-374-OdIWl95jNxKcseZbzML-Iw-1; Tue, 16 Nov 2021 12:23:54 -0500 X-MC-Unique: OdIWl95jNxKcseZbzML-Iw-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 3219C804142; Tue, 16 Nov 2021 17:23:53 +0000 (UTC) Received: from redhat.com (unknown [10.33.36.48]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 33C2260C0F; Tue, 16 Nov 2021 17:23:40 +0000 (UTC) Date: Tue, 16 Nov 2021 17:23:37 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Tyler Fanelli Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org, mtosatti@redhat.com, armbru@redhat.com, pbonzini@redhat.com, eblake@redhat.com Subject: Re: [PATCH] sev: allow capabilities to check for SEV-ES support Message-ID: Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <20211115193804.294529-1-tfanelli@redhat.com> <26204690-493f-67a8-1791-c9c9d38c0240@redhat.com> <02e72302-8cb3-9268-32bd-57e9423f1590@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <02e72302-8cb3-9268-32bd-57e9423f1590@redhat.com> User-Agent: Mutt/2.0.7 (2021-05-04) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, Nov 16, 2021 at 11:58:12AM -0500, Tyler Fanelli wrote: > On 11/16/21 10:53 AM, Daniel P. Berrangé wrote: > > On Tue, Nov 16, 2021 at 10:29:35AM -0500, Tyler Fanelli wrote: > > > On 11/16/21 4:17 AM, Daniel P. Berrangé wrote: > > > > On Mon, Nov 15, 2021 at 02:38:04PM -0500, Tyler Fanelli wrote: > > > > > Probe for SEV-ES and SEV-SNP capabilities to distinguish between Rome, > > > > > Naples, and Milan processors. Use the CPUID function to probe if a > > > > > processor is capable of running SEV-ES or SEV-SNP, rather than if it > > > > > actually is running SEV-ES or SEV-SNP. > > > > > > > > > > Signed-off-by: Tyler Fanelli > > > > > --- > > > > > qapi/misc-target.json | 11 +++++++++-- > > > > > target/i386/sev.c | 6 ++++-- > > > > > 2 files changed, 13 insertions(+), 4 deletions(-) > > > > > > > > > > diff --git a/qapi/misc-target.json b/qapi/misc-target.json > > > > > index 5aa2b95b7d..c3e9bce12b 100644 > > > > > --- a/qapi/misc-target.json > > > > > +++ b/qapi/misc-target.json > > > > > @@ -182,13 +182,19 @@ > > > > > # @reduced-phys-bits: Number of physical Address bit reduction when SEV is > > > > > # enabled > > > > > # > > > > > +# @es: SEV-ES capability of the machine. > > > > > +# > > > > > +# @snp: SEV-SNP capability of the machine. > > > > > +# > > > > > # Since: 2.12 > > > > > ## > > > > > { 'struct': 'SevCapability', > > > > > 'data': { 'pdh': 'str', > > > > > 'cert-chain': 'str', > > > > > 'cbitpos': 'int', > > > > > - 'reduced-phys-bits': 'int'}, > > > > > + 'reduced-phys-bits': 'int', > > > > > + 'es': 'bool', > > > > > + 'snp': 'bool'}, > > > > > 'if': 'TARGET_I386' } > > > > > ## > > > > > @@ -205,7 +211,8 @@ > > > > > # > > > > > # -> { "execute": "query-sev-capabilities" } > > > > > # <- { "return": { "pdh": "8CCDD8DDD", "cert-chain": "888CCCDDDEE", > > > > > -# "cbitpos": 47, "reduced-phys-bits": 5}} > > > > > +# "cbitpos": 47, "reduced-phys-bits": 5 > > > > > +# "es": false, "snp": false}} > > > > We've previously had patches posted to support SNP in QEMU > > > > > > > > https://lists.gnu.org/archive/html/qemu-devel/2021-08/msg04761.html > > > > > > > > and this included an update to query-sev for reporting info > > > > about the VM instance. > > > > > > > > Your patch is updating query-sev-capabilities, which is a > > > > counterpart for detecting host capabilities separate from > > > > a guest instance. > > > Yes, that's because with this patch, I'm more interested in determining > > > which AMD processor is running on a host, and less if ES or SNP is actually > > > running on a guest instance or not. > > > > None the less I wonder if the same design questions from > > > > query-sev apply. ie do we need to have the ability to > > > > report any SNP specific information fields, if so we need > > > > to use a discriminated union of structs, not just bool > > > > flags. > > > > > > > > More generally I'm some what wary of adding this to > > > > query-sev-capabilities at all, unless it is part of the > > > > main SEV-SNP series. > > > > > > > > Also what's the intended usage for the mgmt app from just > > > > having these boolean fields ? Are they other more explicit > > > > feature flags we should be reporting, instead of what are > > > > essentially SEV generation codenames. > > > If by "mgmt app" you're referring to sevctl, in order to determine which > > > certificate chain to use (Naples vs Rome vs Milan ARK/ASK) we must query > > > which processor we are running on. Although sevctl has a feature which can > > > do this already, we cannot guarantee that sevctl is running on the same host > > > that a VM is running on, so we must query this capability from QEMU. My > > > logic was determining the processor would have been the following: > > I'm not really talking about a specific, rather any tool which wants > > to deal with SEV and QEMU, whether libvirt or an app using libvirt, > > or something else using QEMU directly. > > Ah, my mistake. > > > Where does the actual cert chain payload come from ? Is that something > > the app has to acquire out of band, or can the full cert chain be > > acquired from the hardware itself ? > > The cert chain (or the ARK/ASK specifically) comes from AMD's KDS, yet > sevctl is able to cache the values, and has them on-hand when needed. This > patch would tell sevctl *which* of the cert chains to use (Naples vs Rome vs > Milan chain). If need be, I could just focus on Naples and Rome processors > for now and bring support for SNP (Milan processors) later on when it is > more mature. > > > > !es && !snp --> Naples > > > > > > es && !snp --> Rome > > > > > > es && snp --> Milan > > This approach isn't future proof if subsequent generations introduce > > new certs. It feels like we should be explicitly reporting something > > about the certs rather than relying on every app to re-implement tihs > > logic. > > Alright, like an encoding of which processor generation the host is running > on? IIUC (from looking at sev-tool), the certificates can be acquired from https://developer.amd.com/wp-content/resources/ask_ark_{gen}.cert where {gen} is one of "milan", "naples", "rome". With this in mind, I'd think that query-sev-capabilities could just report the required certificate name. e.g. { 'enum': 'SevAskArkCertName', 'data': ['milan', 'naples', 'rome'] } and then report it in SevCapability struct with "ask-ark-cert-name": "SevAskArkCertName" 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 :|