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 lists1p.gnu.org (lists1p.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 470F6C79FAD for ; Wed, 9 Sep 2026 06:21:32 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1x4Bfw-0007Uh-Cw; Wed, 09 Sep 2026 02:20:52 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1x4Bfu-0007U7-Gt for qemu-devel@nongnu.org; Wed, 09 Sep 2026 02:20:50 -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 1x4Bfs-0003jE-Et for qemu-devel@nongnu.org; Wed, 09 Sep 2026 02:20:50 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1788934846; h=from:from: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=y6r5aoobcqd9F4eMSuFquKXONNVH+X/rcsYMSKawr+0=; b=gigKPfiZE6mndcsGvng7emBXwZ3a67vopyfeRS1FDZ+3Mof4cfggB+XjhUtqgiN+G4ZPAI r6+ozugC5MZBUD7ib7d/VyrS+MlAtkZyhLZBpXAfQiH4Ia4KHdXkKB0ToY8e5bM8L1Nu9v O6o0sk47Nv3K42q/XPVIGCyudA7MUn8= Received: from mx-prod-mc-03.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-679-tooLIFfbOJCgtj55566jAA-1; Wed, 09 Sep 2026 02:20:41 -0400 X-MC-Unique: tooLIFfbOJCgtj55566jAA-1 X-Mimecast-MFC-AGG-ID: tooLIFfbOJCgtj55566jAA_1788934839 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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id B9AB81955DDD; Wed, 9 Sep 2026 06:20:39 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.44.22.5]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id DB8B0195608C; Wed, 9 Sep 2026 06:20:38 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 7FEA121E6A04; Wed, 09 Sep 2026 08:20:36 +0200 (CEST) From: Markus Armbruster To: Michael Roth Cc: , , , , , , , , , , , Subject: Re: [PATCH v2 07/19] accel/kvm: Add CGS option to control in-place conversion support In-Reply-To: <20260908205236.838281-8-michael.roth@amd.com> (Michael Roth's message of "Tue, 8 Sep 2026 15:48:27 -0500") References: <20260908205236.838281-1-michael.roth@amd.com> <20260908205236.838281-8-michael.roth@amd.com> Date: Wed, 09 Sep 2026 08:20:36 +0200 Message-ID: <878q5bosi3.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 12 X-Spam_score: 1.2 X-Spam_bar: + X-Spam_report: (1.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_H2=0.001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_PASS=-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: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Michael Roth writes: > For confidential guests, guest_memfd is currently used only for private > guest memory, and normal guest memory comes from the configured memory > backend just as it does for a non-confidential guest. It is now possible > to use the same physical memory to back a particular GPA regardless of > whether it is in a shared or private state. This avoids the need to > rely on discarding memory between shared/private conversions (to avoid > doubled memory usage), and is intended to be the primary mode of using > guest_memfd for confidential guests moving forward, and future features > like hugepage support will likely require it. > > Add an option to enable this support. Since ConfidentialGuestSupport is > already used to track some guest_memfd-related functionality (e.g. > whether it is required for the configured machine), similarly introduce > this option as a property of ConfidentialGuestSupport. > > Also add the KVM-specific checks to enable this support, but leave the > option disabled until other required changes are implemented for > CGS variants that intend to make use of KVM's in-place conversion > support. > > While technically the convert-in-place option could be introduced as an > SEV-specific option, it is a given that TDX will also be introducing > in-place conversion support based on the same guest_memfd kernel > infrastructure, so introduce it via a new > ConfidentialGuestSupportProperties base class that other confidential VM > implementations can utilized for common options. > > Signed-off-by: Michael Roth [...] > diff --git a/qapi/qom.json b/qapi/qom.json > index 909add4299..20d6fefb04 100644 > --- a/qapi/qom.json > +++ b/qapi/qom.json > @@ -1005,6 +1005,21 @@ > 'if': 'CONFIG_IGVM', > 'data': { 'file': 'str' } } > > +## > +# @ConfidentialGuestSupportProperties: > +# > +# Properties for ConfidentialGuestSupport base class. > +# > +# @convert-in-place: If true, the same physical pages are reused > +# when memory is converted between shared and private states. > +# If false (default), separate allocations are used depending > +# on whether the page is private or shared. Any guidance on when to enable @convert-in-place? > +# > +# Since: 11.2 > +## > +{ 'struct': 'ConfidentialGuestSupportProperties', > + 'data': { '*convert-in-place': 'bool' } } > + > ## > # @SevCommonProperties: > # > @@ -1033,6 +1048,7 @@ > # Since: 9.1 > ## > { 'struct': 'SevCommonProperties', > + 'base': 'ConfidentialGuestSupportProperties', > 'data': { '*sev-device': 'str', > '*cbitpos': 'uint32', > 'reduced-phys-bits': 'uint32', Can you explain why you put @convert-in-place into a new base type instead of right here?