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 36A96C2BD05 for ; Mon, 24 Jun 2024 11:44:59 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sLi7O-0004AM-Cc; Mon, 24 Jun 2024 07:44:18 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sLi7K-0004A1-Ps for qemu-devel@nongnu.org; Mon, 24 Jun 2024 07:44:14 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sLi7I-0001zR-75 for qemu-devel@nongnu.org; Mon, 24 Jun 2024 07:44:13 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1719229450; 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=cXMlOCTBH9ppGiREvrYGHGuZ92vyek5UuwObkNJ0g1I=; b=eeKOOHDZh07WDTcDJnjClw+8N2uncTb3omUxVKfuDez2FDFSWeGNqr06fVqTmjOsmgZjHF BRPgdS4u1/WOsbPKiGzAiKAfBjcL0veSTBBad6Y9u2qgH+WshTp+TkUUmSUkjYr+x+x4fC RA9mfWnRbMM9QtRzpbhMS6OfGq6vcnQ= Received: from mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-193-cK_p3YuiMISorwLMxdqKRw-1; Mon, 24 Jun 2024 07:44:07 -0400 X-MC-Unique: cK_p3YuiMISorwLMxdqKRw-1 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 54B071956089; Mon, 24 Jun 2024 11:44:06 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.226]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 8B2001954B13; Mon, 24 Jun 2024 11:44:01 +0000 (UTC) Date: Mon, 24 Jun 2024 12:43:57 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: qemu-devel@nongnu.org Cc: Paolo Bonzini , Michael Roth , Eduardo Habkost , Richard Henderson , Marcel Apfelbaum , "Michael S. Tsirkin" , kvm@vger.kernel.org, Markus Armbruster , Eric Blake , Marcelo Tosatti Subject: Re: [PATCH] i386: revert defaults to 'legacy-vm-type=true' for SEV(-ES) guests Message-ID: References: <20240614103924.1420121-1-berrange@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20240614103924.1420121-1-berrange@redhat.com> User-Agent: Mutt/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 10 X-Spam_score: 1.0 X-Spam_bar: + X-Spam_report: (1.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.207, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Ping, any comments for this ? On Fri, Jun 14, 2024 at 11:39:24AM +0100, Daniel P. Berrangé wrote: > The KVM_SEV_INIT2 ioctl was only introduced in Linux 6.10, which will > only have been released for a bit over a month when QEMU 9.1 is > released. > > The SEV(-ES) support in QEMU has been present since 2.12 dating back > to 2018. With this in mind, the overwhealming majority of users of > SEV(-ES) are unlikely to be running Linux >= 6.10, any time in the > forseeable future. > > IOW, defaulting new QEMU to 'legacy-vm-type=false' means latest QEMU > machine types will be broken out of the box for most SEV(-ES) users. > Even if the kernel is new enough, it also affects the guest measurement, > which means that their existing tools for validating measurements will > also be broken by the new default. > > This is not a sensible default choice at this point in time. Revert to > the historical behaviour which is compatible with what most users are > currently running. > > This can be re-evaluated a few years down the line, though it is more > likely that all attention will be on SEV-SNP by this time. Distro > vendors may still choose to change this default downstream to align > with their new major releases where they can guarantee the kernel > will always provide the required functionality. > > Signed-off-by: Daniel P. Berrangé > --- > hw/i386/pc.c | 1 - > qapi/qom.json | 12 ++++++------ > target/i386/sev.c | 7 +++++++ > 3 files changed, 13 insertions(+), 7 deletions(-) > > diff --git a/hw/i386/pc.c b/hw/i386/pc.c > index 0469af00a7..b65843c559 100644 > --- a/hw/i386/pc.c > +++ b/hw/i386/pc.c > @@ -82,7 +82,6 @@ > GlobalProperty pc_compat_9_0[] = { > { TYPE_X86_CPU, "x-l1-cache-per-thread", "false" }, > { TYPE_X86_CPU, "guest-phys-bits", "0" }, > - { "sev-guest", "legacy-vm-type", "true" }, > { TYPE_X86_CPU, "legacy-multi-node", "on" }, > }; > const size_t pc_compat_9_0_len = G_N_ELEMENTS(pc_compat_9_0); > diff --git a/qapi/qom.json b/qapi/qom.json > index 8bd299265e..714ebeec8b 100644 > --- a/qapi/qom.json > +++ b/qapi/qom.json > @@ -912,12 +912,12 @@ > # @handle: SEV firmware handle (default: 0) > # > # @legacy-vm-type: Use legacy KVM_SEV_INIT KVM interface for creating the VM. > -# The newer KVM_SEV_INIT2 interface syncs additional vCPU > -# state when initializing the VMSA structures, which will > -# result in a different guest measurement. Set this to > -# maintain compatibility with older QEMU or kernel versions > -# that rely on legacy KVM_SEV_INIT behavior. > -# (default: false) (since 9.1) > +# The newer KVM_SEV_INIT2 interface, from Linux >= 6.10, syncs > +# additional vCPU state when initializing the VMSA structures, > +# which will result in a different guest measurement. Toggle > +# this to control compatibility with older QEMU or kernel > +# versions that rely on legacy KVM_SEV_INIT behavior. > +# (default: true) (since 9.1) > # > # Since: 2.12 > ## > diff --git a/target/i386/sev.c b/target/i386/sev.c > index 004c667ac1..16029282b7 100644 > --- a/target/i386/sev.c > +++ b/target/i386/sev.c > @@ -2086,6 +2086,13 @@ sev_guest_instance_init(Object *obj) > object_property_add_uint32_ptr(obj, "policy", &sev_guest->policy, > OBJ_PROP_FLAG_READWRITE); > object_apply_compat_props(obj); > + > + /* > + * KVM_SEV_INIT2 was only introduced in Linux 6.10. Avoid > + * breaking existing users of SEV, since the overwhealming > + * majority won't have a new enough kernel for a long time > + */ > + sev_guest->legacy_vm_type = true; > } > > /* guest info specific sev/sev-es */ > -- > 2.45.1 > 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 :|