From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45643) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fb7ls-0002x8-MA for qemu-devel@nongnu.org; Thu, 05 Jul 2018 13:10:21 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fb7lo-00076n-Lr for qemu-devel@nongnu.org; Thu, 05 Jul 2018 13:10:20 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:41888 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fb7lo-00076T-GT for qemu-devel@nongnu.org; Thu, 05 Jul 2018 13:10:16 -0400 Date: Thu, 5 Jul 2018 20:10:15 +0300 From: "Michael S. Tsirkin" Message-ID: <20180705200659-mutt-send-email-mst@kernel.org> References: <20180705123929.GB16293@redhat.com> <20180705125231.GD16293@redhat.com> <20180705164343.GE16293@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180705164343.GE16293@redhat.com> Subject: Re: [Qemu-devel] Byte ordering of VM Generation ID in Windows VMs List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Richard W.M. Jones" Cc: Laszlo Ersek , qemu-devel@nongnu.org, berrange@redhat.com, jferlan@redhat.com, ben@skyportsystems.com On Thu, Jul 05, 2018 at 05:43:43PM +0100, Richard W.M. Jones wrote: > On Thu, Jul 05, 2018 at 04:20:33PM +0200, Laszlo Ersek wrote: > > QEMU does the right thing. If other hypervisors don't do this -- while > > still taking and displaying the value in UUID / GUID textual format --, > > they are wrong. The VMGENID spec from Microsoft > > specifically mentions > > "GUID". > > The MSFT spec does mention GUID, but it seems to me that it's only > using GUID as an incidental example -- ie. that you might use the VM > Generation ID to generate a GUID. Outside that example it > consistently refers to the VM Gen ID as a 128-bit integer. It also > says that it could be used as a "high entropy random data source", > which is not in fact true if it's a UUID. > > It has to be said that after reading the spec again [the MSFT spec, > not qemu's spec] and what other hypervisors are doing, I'm not sure > qemu is doing the right thing here. > > Rich. So right now we have a "GUID" property. We could always add an alternative property for people who want to treat the ID as an integer. Would that address the issue? > -- > Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones > Read my programming and virtualization blog: http://rwmj.wordpress.com > libguestfs lets you edit virtual machines. Supports shell scripting, > bindings from many languages. http://libguestfs.org