From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 88C003FE36E for ; Mon, 27 Jul 2026 18:23:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785176618; cv=none; b=uY24rGN8NBxHC6jCS6t9sh+zabEtyUREQXL+ssQDCfEBsISS5HGxTbprQ3ZmmE337BYIrMjOzs7ecOAAEhrEFnM7RaYKBlM4pdClnYQWP5SbM5R0287ZB/DyOW3RYarTFZP29uJBJJL8yQbPHMesLm4IoUKGVW1a6tc5UOnQn1A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785176618; c=relaxed/simple; bh=ZXDlJ8n3xPDBjhT4EY3xq+fK/7i5VAnTGhoZVp2UdkA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=IX/1sQbbzoFSLa/iZPrwSxz9b1qFynPQMadMhOf+ztOnBKyZ+9+X9HZvnd7phbUulWGUgFDT9t9WP4dr2ezdRC9jWbN5Wh+pc4OCkcw8GtMjAMcAXhvUpHhsxqEn3VWNkqT353BAaBfjs8JH1cpQN/bYImycd07tixj/qoll1OQ= 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=IjTQOBE9; arc=none smtp.client-ip=170.10.133.124 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="IjTQOBE9" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1785176615; 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=ZXDlJ8n3xPDBjhT4EY3xq+fK/7i5VAnTGhoZVp2UdkA=; b=IjTQOBE9Wx5HnHfdk0Tc+vu2UILsL/Zu1VhlYV0mSsZaRaTEkn5DzF2OCuPx/1uNhDydef AW+1SWTyWYC27/P/X5sVeDLSiP2GwN/8LnorqRSFSkiwkfJDO2R1rBuRSCqMqFOH7EAC22 pvusbyZAbzT0PRUAM6S1V928np6vM+k= Received: from mx-prod-mc-05.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-290-LVGBbTrvN66hTohZ7yIYHQ-1; Mon, 27 Jul 2026 14:23:32 -0400 X-MC-Unique: LVGBbTrvN66hTohZ7yIYHQ-1 X-Mimecast-MFC-AGG-ID: LVGBbTrvN66hTohZ7yIYHQ_1785176609 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (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-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 3AE5A195E909; Mon, 27 Jul 2026 18:23:28 +0000 (UTC) Received: from localhost (unknown [10.2.16.116]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id A7A5530010D0; Mon, 27 Jul 2026 18:23:25 +0000 (UTC) Date: Mon, 27 Jul 2026 14:23:24 -0400 From: Stefan Hajnoczi To: Akihiko Odaki Cc: ConKite , qemu-devel@nongnu.org, "Michael S. Tsirkin" , Stefano Garzarella , Alex =?iso-8859-1?Q?Benn=E9e?= , Viresh Kumar , Gerd Hoffmann , Mathieu Poirier , Manos Pitsidianakis , Haixu Cui , Raphael Norwitz , Kevin Wolf , Hanna Reitz , =?iso-8859-1?Q?Marc-Andr=E9?= Lureau , Paolo Bonzini , Fam Zheng , Milan Zamazal , Dmitry Osipenko , qemu-block@nongnu.org, virtio-fs@lists.linux.dev, "Gonglei (Arei)" , zhenwei pi , Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , Eric Blake , Markus Armbruster , Jason Wang , Peter Xu , Eugenio =?iso-8859-1?Q?P=E9rez?= , Alyssa Ross , Demi Marie Obenour Subject: Re: [PATCH RFC 00/15] vhost-user: isolated memory Message-ID: <20260727182324.GA371693@fedora> References: <20260723-vhost-user-isolated-memory-v1-0-6b97c439eb28@gmail.com> Precedence: bulk X-Mailing-List: virtio-fs@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="7gZyb6NXvQiWaoF9" Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 --7gZyb6NXvQiWaoF9 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sat, Jul 25, 2026 at 12:45:08PM +0900, Akihiko Odaki wrote: > I also hope this could fix vhost-user for TCG: > https://gitlab.com/qemu-project/qemu/-/work_items/2092 >=20 > Perhaps the memory isolation should be enabled by default for TCG. If I understand the bug correctly, TCG needs the dirty bitmap to be up-to-date and vhost-user's dirty logging mechanism does not suffice. Memory isolation would keep the dirty bitmap up-to-date but copying data between guest RAM and the isolated memory would add overhead. For the TCG use case it should be possible to use just vhost-shadow-virtqueue.c without isolated memory so that vhost_svq_flush() -> virtqueue_fill() -> virtqueue_unmap_sg() -> dma_memory_unmap() keeps the dirty bitmap updated. There is still an overhead because the virtqueue kick/call is intercepted by QEMU, but there is no memcpy. The TCG use case is something that could be tackled once memory isolation is finished. If no one has time to implement the pure svq solution for TCG, then memory isolation could be used in any case. 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