From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37986) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fb7MF-0006PD-3J for qemu-devel@nongnu.org; Thu, 05 Jul 2018 12:43:52 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fb7MB-0003uX-Lx for qemu-devel@nongnu.org; Thu, 05 Jul 2018 12:43:50 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37126) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fb7MB-0003u8-Fs for qemu-devel@nongnu.org; Thu, 05 Jul 2018 12:43:47 -0400 Received: from smtp.corp.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.26]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B62C2317C40A for ; Thu, 5 Jul 2018 16:43:46 +0000 (UTC) Date: Thu, 5 Jul 2018 17:43:43 +0100 From: "Richard W.M. Jones" Message-ID: <20180705164343.GE16293@redhat.com> References: <20180705123929.GB16293@redhat.com> <20180705125231.GD16293@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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: Laszlo Ersek Cc: qemu-devel@nongnu.org, mst@redhat.com, berrange@redhat.com, jferlan@redhat.com 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. -- 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