From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D702A33D6ED for ; Wed, 9 Sep 2026 06:20:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788934847; cv=none; b=Tco6kw0kz1v0W2PGJWDkfN7IEIHmZfgHPz6ReXnMwVbtHT4aSYyb28xSy3xZbJ+R6sbkDsQfm2+Co22EOb3ezAUFOT1tUEJSt0WLwId8s1Wuny5gkUX/rk+lAfTDexcci+o+QTp8GmlKMIMQzE40SHJRrzZ0HxuT4RTAu8nEWns= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788934847; c=relaxed/simple; bh=KgAH5DFo1fynH3JhTed3whC3C2h490xYMaD/jxMaETI=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=riDqkQ4SChdoOYztGs9iqN+rDaPcdLelNix6OztaQDG5Dve+yNWaE4ixHNwi4Qlb7gfWWEE/PIlo1epCtch/HqoxwfzOHrAzWRdFrprrogoUHdezO+cBCi6DfUhJAEksCmToXpSgzed9jx+sykI3TD7AlCL35ADtB/gBQdorIIU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=hU2YWRgL; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="hU2YWRgL" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1788934842; 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=hU2YWRgL+2txJnKZEHuzJdMKC/U8y2MRfd0BfNNoPGFOhnHpdF/aWV/cUAQysMrTVKC6x1 8gFcEdVee6M9BoJX1WuaToKlhUmu+PSwAd2L7y3sFgZx0PQpTIxEUmcXuvhb97oa1k3xs0 2t6rBL8FMSUuXJEdssKut+1QDP0eTh8= 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) Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 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?