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 6555CC433EF for ; Thu, 24 Feb 2022 08:26:16 +0000 (UTC) Received: from localhost ([::1]:33036 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nN9S3-000211-2c for qemu-devel@archiver.kernel.org; Thu, 24 Feb 2022 03:26:15 -0500 Received: from eggs.gnu.org ([209.51.188.92]:41410) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nN9PO-0001HQ-C9 for qemu-devel@nongnu.org; Thu, 24 Feb 2022 03:23:30 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:37810) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nN9PJ-0004yy-8W for qemu-devel@nongnu.org; Thu, 24 Feb 2022 03:23:27 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1645691004; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=IIw6thHsE5mKcntqaPXG9e+eptGC30Zi7cXPp7mndxI=; b=Z4EqFzzDGxCpXeswZZFV9Q8f7SHkLVWPpWC15J4I1bEmXBxEmaEVv1j2FL4q3bouxMBSEK QZrLnFajwFycYWtM1kGQ3fgPCDTPt2BAi2qFMbZxD43w/ZuKcimvmYVqaJ8XTfeW88XhFw CRTGUB6Nj9NxFApGGYK64+NUJJz+mYw= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-633-xY8ajeExNjqKwLBHAp-9EQ-1; Thu, 24 Feb 2022 03:23:20 -0500 X-MC-Unique: xY8ajeExNjqKwLBHAp-9EQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 991471854E26; Thu, 24 Feb 2022 08:23:17 +0000 (UTC) Received: from lacos-laptop-7.usersys.redhat.com (unknown [10.39.194.86]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C47FB7AB5F; Thu, 24 Feb 2022 08:22:52 +0000 (UTC) Subject: Re: [PATCH RFC v1 0/2] VM fork detection for RNG To: "Jason A. Donenfeld" , LKML , Linux Crypto Mailing List , QEMU Developers , KVM list , linux-s390@vger.kernel.org, adrian@parity.io References: <20220223131231.403386-1-Jason@zx2c4.com> From: Laszlo Ersek Message-ID: <2653b6c7-a851-7a48-f1f8-3bde742a0c9f@redhat.com> Date: Thu, 24 Feb 2022 09:22:50 +0100 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Received-SPF: pass client-ip=170.10.129.124; envelope-from=lersek@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham 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: , Cc: Theodore Ts'o , ehabkost@redhat.com, ben@skyportsystems.com, Jann Horn , Greg Kroah-Hartman , "Michael S. Tsirkin" , "Weiss, Radu" , "=?UTF-8?Q?Daniel_P._Berrang=c3=a9?=" , "Richard W.M. Jones" , "Catangiu, Adrian Costin" , graf@amazon.com, Igor Mammedov , Colm MacCarthaigh , "Singh, Balbir" , "Woodhouse, David" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" (+Daniel, +Rich) On 02/23/22 17:08, Jason A. Donenfeld wrote: > On Wed, Feb 23, 2022 at 2:12 PM Jason A. Donenfeld wrote: >> second patch is the reason this is just an RFC: it's a cleanup of the >> ACPI driver from last year, and I don't really have much experience >> writing, testing, debugging, or maintaining these types of drivers. >> Ideally this thread would yield somebody saying, "I see the intent of >> this; I'm happy to take over ownership of this part." That way, I can >> focus on the RNG part, and whoever steps up for the paravirt ACPI part >> can focus on that. > > I actually managed to test this in QEMU, and it seems to work quite well. Steps: > > $ qemu-system-x86_64 ... -device vmgenid,guid=auto -monitor stdio > (qemu) savevm blah > (qemu) quit > $ qemu-system-x86_64 ... -device vmgenid,guid=auto -monitor stdio > (qemu) loadvm blah > > Doing this successfully triggers the function to reinitialize the RNG > with the new GUID. QEMU's related design is documented in . The Microsoft specification referenced therein, , contains the following statement: "they can also use the data provided in the 128-bit identifier as a high entropy random data source" So reinitializing an RNG from it is an express purpose. More info in the libvirt docs (see "genid"): https://libvirt.org/formatdomain.html#general-metadata QEMU's interpretation of the VMGENID specifically as a UUID (which I believe comes from me) has received (valid) criticism since: https://github.com/libguestfs/virt-v2v/blob/master/docs/vm-generation-id-across-hypervisors.txt (This document also investigates VMGENID on other hypervisors, which I think pertains to your other message.) > (It appears there's a bug in QEMU which prevents > the GUID from being reinitialized when running `loadvm` without > quitting first; I suppose this should be discussed with QEMU > upstream.) That's not (necessarily) a bug; see the end of the above-linked QEMU document: "There are no known use cases for changing the GUID once QEMU is running, and adding this capability would greatly increase the complexity." > > So that's very positive. But I would appreciate hearing from some > ACPI/Virt/Amazon people about this. I've only made some random comments; I didn't see a question so I couldn't attempt to answer :) Thanks Laszlo